\documentclass[10pt,a4paper]{article} % Packages \usepackage{fancyhdr} % For header and footer \usepackage{multicol} % Allows multicols in tables \usepackage{tabularx} % Intelligent column widths \usepackage{tabulary} % Used in header and footer \usepackage{hhline} % Border under tables \usepackage{graphicx} % For images \usepackage{xcolor} % For hex colours %\usepackage[utf8x]{inputenc} % For unicode character support \usepackage[T1]{fontenc} % Without this we get weird character replacements \usepackage{colortbl} % For coloured tables \usepackage{setspace} % For line height \usepackage{lastpage} % Needed for total page number \usepackage{seqsplit} % Splits long words. %\usepackage{opensans} % Can't make this work so far. Shame. Would be lovely. \usepackage[normalem]{ulem} % For underlining links % Most of the following are not required for the majority % of cheat sheets but are needed for some symbol support. \usepackage{amsmath} % Symbols \usepackage{MnSymbol} % Symbols \usepackage{wasysym} % Symbols %\usepackage[english,german,french,spanish,italian]{babel} % Languages % Document Info \author{AviMaths (AviMathPerson)} \pdfinfo{ /Title (discrete-math.pdf) /Creator (Cheatography) /Author (AviMaths (AviMathPerson)) /Subject (Discrete Math Cheat Sheet) } % Lengths and widths \addtolength{\textwidth}{6cm} \addtolength{\textheight}{-1cm} \addtolength{\hoffset}{-3cm} \addtolength{\voffset}{-2cm} \setlength{\tabcolsep}{0.2cm} % Space between columns \setlength{\headsep}{-12pt} % Reduce space between header and content \setlength{\headheight}{85pt} % If less, LaTeX automatically increases it \renewcommand{\footrulewidth}{0pt} % Remove footer line \renewcommand{\headrulewidth}{0pt} % Remove header line \renewcommand{\seqinsert}{\ifmmode\allowbreak\else\-\fi} % Hyphens in seqsplit % This two commands together give roughly % the right line height in the tables \renewcommand{\arraystretch}{1.3} \onehalfspacing % Commands \newcommand{\SetRowColor}[1]{\noalign{\gdef\RowColorName{#1}}\rowcolor{\RowColorName}} % Shortcut for row colour \newcommand{\mymulticolumn}[3]{\multicolumn{#1}{>{\columncolor{\RowColorName}}#2}{#3}} % For coloured multi-cols \newcolumntype{x}[1]{>{\raggedright}p{#1}} % New column types for ragged-right paragraph columns \newcommand{\tn}{\tabularnewline} % Required as custom column type in use % Font and Colours \definecolor{HeadBackground}{HTML}{333333} \definecolor{FootBackground}{HTML}{666666} \definecolor{TextColor}{HTML}{333333} \definecolor{DarkBackground}{HTML}{3014A3} \definecolor{LightBackground}{HTML}{F2F0F9} \renewcommand{\familydefault}{\sfdefault} \color{TextColor} % Header and Footer \pagestyle{fancy} \fancyhead{} % Set header to blank \fancyfoot{} % Set footer to blank \fancyhead[L]{ \noindent \begin{multicols}{3} \begin{tabulary}{5.8cm}{C} \SetRowColor{DarkBackground} \vspace{-7pt} {\parbox{\dimexpr\textwidth-2\fboxsep\relax}{\noindent \hspace*{-6pt}\includegraphics[width=5.8cm]{/web/www.cheatography.com/public/images/cheatography_logo.pdf}} } \end{tabulary} \columnbreak \begin{tabulary}{11cm}{L} \vspace{-2pt}\large{\bf{\textcolor{DarkBackground}{\textrm{Discrete Math Cheat Sheet}}}} \\ \normalsize{by \textcolor{DarkBackground}{AviMaths (AviMathPerson)} via \textcolor{DarkBackground}{\uline{cheatography.com/189338/cs/42865/}}} \end{tabulary} \end{multicols}} \fancyfoot[L]{ \footnotesize \noindent \begin{multicols}{3} \begin{tabulary}{5.8cm}{LL} \SetRowColor{FootBackground} \mymulticolumn{2}{p{5.377cm}}{\bf\textcolor{white}{Cheatographer}} \\ \vspace{-2pt}AviMaths (AviMathPerson) \\ \uline{cheatography.com/avimathperson} \\ \uline{\seqsplit{unitmeasure}.xyz} \end{tabulary} \vfill \columnbreak \begin{tabulary}{5.8cm}{L} \SetRowColor{FootBackground} \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Cheat Sheet}} \\ \vspace{-2pt}Published 27th March, 2024.\\ Updated 27th March, 2024.\\ Page {\thepage} of \pageref{LastPage}. \end{tabulary} \vfill \columnbreak \begin{tabulary}{5.8cm}{L} \SetRowColor{FootBackground} \mymulticolumn{1}{p{5.377cm}}{\bf\textcolor{white}{Sponsor}} \\ \SetRowColor{white} \vspace{-5pt} %\includegraphics[width=48px,height=48px]{dave.jpeg} Measure your website readability!\\ www.readability-score.com \end{tabulary} \end{multicols}} \begin{document} \raggedright \raggedcolumns % Set font size to small. Switch to any value % from this page to resize cheat sheet text: % www.emerson.emory.edu/services/latex/latex_169.html \footnotesize % Small font. \begin{multicols*}{3} \begin{tabularx}{5.377cm}{x{1.29402 cm} x{3.68298 cm} } \SetRowColor{DarkBackground} \mymulticolumn{2}{x{5.377cm}}{\bf\textcolor{white}{Important relations}} \tn % Row 0 \SetRowColor{LightBackground} \seqsplit{Reflexive:} & Shorthand: Ia ⊆ R Meaning: Every element is related to itself. for all a ∈ A, aRa holds ( R ⊆ \{(a, a) | a ∈ A\} ) \tn % Row Count 5 (+ 5) % Row 1 \SetRowColor{white} \seqsplit{Transitive:} & Shorthand: ( R ∘ R = R2 ⊆ R ) Meaning: If ( (a, b) ∈ R ) and ( (b, c) ∈ R ), then ( (a, c) ∈ R ). (aRb and bRc) -\textgreater{} aRc \tn % Row Count 10 (+ 5) % Row 2 \SetRowColor{LightBackground} \seqsplit{Symmetric:} & Shorthand: ( R = R⁻$^{\textrm{1}}$ ) Meaning: If ( (a, b) ∈ R ), then ( (b, a) ∈ R ). When aRb \textless{}=\textgreater{} bRa \tn % Row Count 14 (+ 4) % Row 3 \SetRowColor{white} \seqsplit{Antisymmetric:} & Shorthand: ( R ∩ R⁻$^{\textrm{1}}$ ⊆ \{(a, a) | a ∈ A\} ) Meaning: If ( (a, b) ∈ R ) and ( (b, a) ∈ R ), then ( a = b ). (aRb and bRa) -\textgreater{} (a = b) - This does not mean not-symmetric \tn % Row Count 21 (+ 7) \hhline{>{\arrayrulecolor{DarkBackground}}--} \SetRowColor{LightBackground} \mymulticolumn{2}{x{5.377cm}}{Equivalence relation is one where Reflexivity, Transitivity, and Symmetry all hold} \tn \hhline{>{\arrayrulecolor{DarkBackground}}--} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Cardinality}} \tn % Row 0 \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Cardinality} \tn % Row Count 1 (+ 1) % Row 1 \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Aleph 0} \tn % Row Count 2 (+ 1) % Row 2 \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Aleph} \tn % Row Count 3 (+ 1) % Row 3 \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Finite} \tn % Row Count 4 (+ 1) \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{x{1.60195 cm} x{1.14425 cm} x{1.8308 cm} } \SetRowColor{DarkBackground} \mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Combinatorics}} \tn % Row 0 \SetRowColor{LightBackground} Case: & Order matters & Order doesn't matter \tn % Row Count 2 (+ 2) % Row 1 \SetRowColor{white} With repetition & n\textasciicircum{}k (case 1) & nCk (case 3) \tn % Row Count 4 (+ 2) % Row 2 \SetRowColor{LightBackground} Without repetition & nPk (case 2) & (k+n-1)C(k) (case 4) \tn % Row Count 6 (+ 2) \hhline{>{\arrayrulecolor{DarkBackground}}---} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Functions}} \tn % Row 0 \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Let f,g be two functions, (f:A -\textgreater{} B) , (g:B -\textgreater{} A)} \tn % Row Count 1 (+ 1) % Row 1 \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Function f} \tn % Row Count 2 (+ 1) % Row 2 \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Onto} \tn % Row Count 3 (+ 1) % Row 3 \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{One to One} \tn % Row Count 4 (+ 1) % Row 4 \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Onto and One to One} \tn % Row Count 5 (+ 1) % Row 5 \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Identity Ia} \tn % Row Count 6 (+ 1) \hhline{>{\arrayrulecolor{DarkBackground}}-} \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{(g ∘ f)(a) = g(f(a)) means g composed with f} \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Set Theory}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{A ∪ B = \{x ∈ A or x ∈ B or both\} \newline % Row Count 1 (+ 1) A ∩ B = \{x ∈ A and x ∈ B\} \newline % Row Count 2 (+ 1) A ⊕ B = (A - B) ∪ (B - A) = (A ∪ B) - (A ∩ B) \newline % Row Count 4 (+ 2) A - B = A ∩ Bᶜ = \{x ∈ A and x ∉ B\} \newline % Row Count 5 (+ 1) Demorgan's laws: \newline % Row Count 6 (+ 1) (A ∪ B)ᶜ = Aᶜ ∩ Bᶜ \newline % Row Count 7 (+ 1) (A ∩ B)ᶜ = Aᶜ ∪ Bᶜ \newline % Row Count 8 (+ 1) Associativity: \newline % Row Count 9 (+ 1) A ∪ (B ∪ C) = (A ∪ B) ∪ C = A ∪ B ∪ C \newline % Row Count 10 (+ 1) Distributivity; \newline % Row Count 11 (+ 1) A ∪ (B ∩ C) = (A ∪ B) ∩ (A ∪ C) \newline % Row Count 12 (+ 1) A ∩ (B ∪ C) = (A ∩ B) ∪ (A ∩ C)% Row Count 13 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Subsets}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{A ⊆ A ∪ B = B ∪ A \newline % Row Count 1 (+ 1) B ⊆ A ∪ B \newline % Row Count 2 (+ 1) If A ⊆ B, then A ∪ B = B \newline % Row Count 3 (+ 1) A ∩ B ⊆ A ⊆ A ∪ B \newline % Row Count 4 (+ 1) B ∩ A ⊆ B ⊆ A ∪ B% Row Count 5 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Cartesian product:}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{A × B = \{ (a, b) | a ∈ A and b ∈ B \} \newline % Row Count 1 (+ 1) an unordered set of sets of ordered pairs where a is in A, b is in B \newline % Row Count 3 (+ 2) if A = \{1,2\}, B = \{2,3\}, then A × B = \{(1,2), (1,3), (2,2), (2,3)\} \newline % Row Count 5 (+ 2) A × B ≠ B × A (unless A = B) \newline % Row Count 6 (+ 1) A ∩ (A × B) = ∅ \newline % Row Count 7 (+ 1) |A × B| = |A| × |B| \newline % Row Count 8 (+ 1) Distribution: \newline % Row Count 9 (+ 1) A × (B ∪ C) = (A × B) ∪ (A × C) \newline % Row Count 10 (+ 1) A × (B ∩ C) = (A × B) ∩ (A × C)% Row Count 11 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Order relation}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Partial order If and only if all (Reflexivity, Transitivity, and Anti-symmetry) hold \newline % Row Count 2 (+ 2) clear hasse diagram can be drawn \newline % Row Count 3 (+ 1) items for which the relation doesn't hold will be drawn but not connected to the others in the diagram% Row Count 6 (+ 3) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{Total/Linear order: \newline Partial order holds \newline Totality: For any ( a, b ∈ A ), either ( (a, b) ∈ R ) or ( (b, a) ∈ R ). \newline In other words: For any two distinct elements a and b, either a is related to b (a ≤ b), or b is related to a (b ≤ a). \newline hasse diagram would be a straight line (all elements relate to one another in this set)} \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Universal Set}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{Universal Set = U: \newline % Row Count 1 (+ 1) for any finite set A \newline % Row Count 2 (+ 1) U = \{ x ∈ U | x ∉ A \} \newline % Row Count 3 (+ 1) Aᶜ = U - A \newline % Row Count 4 (+ 1) (Aᶜ)ᶜ = A \newline % Row Count 5 (+ 1) Uᶜ = ∅ \newline % Row Count 6 (+ 1) ∅ᶜ = U% Row Count 7 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Relations}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{ARB = (a,b) ∈ R \newline % Row Count 1 (+ 1) Identity: Ia = (a,a) \newline % Row Count 2 (+ 1) Ex: \{(1,1),(2,2),(3,3), … \} \newline % Row Count 3 (+ 1) Relation on set itself: R ⊆ A × A \newline % Row Count 4 (+ 1) ARA is another way to write it too. \newline % Row Count 5 (+ 1) Empty relation when R = ∅ \newline % Row Count 6 (+ 1) implies that the relation R is empty, meaning it does not hold between any two pairs. It's essentially a relation with no elements. \newline % Row Count 9 (+ 3) Complete relation when R = A × B \newline % Row Count 10 (+ 1) implies that the relation R contains all possible pairs that can be formed by taking one element from set A and one element from set B. It's a relation where every element of A is related to every element of B. \newline % Row Count 15 (+ 5) Inverse relation is R⁻$^{\textrm{1}}$ = \{ (b, a) | (a, b) ∈ R \} \newline % Row Count 17 (+ 2) R consists of all pairs in R but with their elements reversed. If (a,b) is in R, then (b,a) is in R⁻$^{\textrm{1}}$ \newline % Row Count 20 (+ 3) Composition of relations: \newline % Row Count 21 (+ 1) R ∘ S = \{ (a, c) | ∃ b : (a, b) ∈ R and (b, c) ∈ S \} \newline % Row Count 23 (+ 2) Set of pairs (a,c) such that exists an element b for which both (a,b) is in R and (b,c) is in S \newline % Row Count 25 (+ 2) R ∘ R = R2 is a relation composed with itself \newline % Row Count 26 (+ 1) (R ∘ S) ∘ T = R ∘ (S ∘ T) i.e it is associative (but not communitive) \newline % Row Count 28 (+ 2) Ia ∘ R = R% Row Count 29 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{p{0.4577 cm} x{2.01388 cm} x{2.10542 cm} } \SetRowColor{DarkBackground} \mymulticolumn{3}{x{5.377cm}}{\bf\textcolor{white}{Order relation terms}} \tn % Row 0 \SetRowColor{LightBackground} \seqsplit{Minimal} & An element a is minimal if there is no b such that b precedes a. & Elements with nothing less than them (no predecessors) \tn % Row Count 4 (+ 4) % Row 1 \SetRowColor{white} \seqsplit{Minimum} & An element a is a minimum if for all b, a precedes b & Element that is less than everything else (either a set has 1 minimum or no minimum element) \tn % Row Count 10 (+ 6) % Row 2 \SetRowColor{LightBackground} \seqsplit{Maximal} & An element a is maximal if there is no b such that a precedes b & follows from minimal (with greater than) \tn % Row Count 14 (+ 4) % Row 3 \SetRowColor{white} \seqsplit{Maximum} & An element a is a maximum if for all b, b precedes a & follows from minimum (with greater than) \tn % Row Count 18 (+ 4) \hhline{>{\arrayrulecolor{DarkBackground}}---} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Power sets}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{The power set of A is denoted as P(A) or 2A \newline % Row Count 1 (+ 1) A ∈ P(A), ∅ ∈ P(A) \newline % Row Count 2 (+ 1) If |A| = n, then |P(A)| = 2n \newline % Row Count 3 (+ 1) |P(A)| = 2|A| \newline % Row Count 4 (+ 1) If A = ∅, then P(A) = \{∅\} \newline % Row Count 5 (+ 1) If A = \{1,2\}, then P(A) = \{∅, \{1\}, \{2\}, \{1, 2\}\} \newline % Row Count 6 (+ 1) |A| \textless{} |P(A)|% Row Count 7 (+ 1) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{Power set proofs}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{P(A) ∩ P(B) = P(A ∩ B) \newline % Row Count 1 (+ 1) Forward Inclusion: Let 𝑋 be an arbitrary element in 𝑃(𝐴) ∩ 𝑃(𝐵). By definition of intersection, 𝑋 belongs to both 𝑃(𝐴) and 𝑃(𝐵). This implies 𝑋 is a subset of both 𝐴 and 𝐵. Consequently, 𝑋 is also a subset of their intersection, 𝐴 ∩ 𝐵. Thus, 𝑋 is an element of 𝑃(𝐴 ∩ 𝐵). Therefore, 𝑃(𝐴) ∩ 𝑃(𝐵) ⊆ 𝑃(𝐴 ∩ 𝐵). \newline % Row Count 9 (+ 8) Reverse Inclusion: Let 𝑌 be an arbitrary element in 𝑃(𝐴 ∩ 𝐵). By definition, 𝑌 is a subset of 𝐴 ∩ 𝐵, hence a subset of both 𝐴 and 𝐵. Consequently, 𝑌 belongs to both 𝑃(𝐴) and 𝑃(𝐵). Thus, 𝑌 is an element of 𝑃(𝐴) ∩ 𝑃(𝐵). Therefore, 𝑃(𝐴 ∩ 𝐵) ⊆ 𝑃(𝐴) ∩ 𝑃(𝐵). \newline % Row Count 16 (+ 7) Conclusion: Combining both directions of inclusion, we've demonstrated that 𝑃(𝐴) ∩ 𝑃(𝐵) ⊆ 𝑃(𝐴 ∩ 𝐵) and 𝑃(𝐴 ∩ 𝐵) ⊆ 𝑃(𝐴) ∩ 𝑃(𝐵), implying 𝑃(𝐴) ∩ 𝑃(𝐵) = 𝑃(𝐴 ∩ 𝐵). Thus, the equality holds.% Row Count 22 (+ 6) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \SetRowColor{LightBackground} \mymulticolumn{1}{x{5.377cm}}{P(A) ∪ P(B) ≠ P(A ∪ B) \newline \newline Example of why these aren't equal: \newline A = \{1\}, B = \{2\}, A ∪ B = \{1,2\} =\textgreater{} P(A ∪ B) = \{∅, \{1\}, \{2\}, \{1,2\}\} \newline \newline P(A) = \{∅, \{1\}\}, P(B) = \{∅, \{2\}\} =\textgreater{} P(A) ∪ P(B) = \{∅, \{1\}, \{2\}\}} \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} \begin{tabularx}{5.377cm}{X} \SetRowColor{DarkBackground} \mymulticolumn{1}{x{5.377cm}}{\bf\textcolor{white}{More combinatorics}} \tn \SetRowColor{white} \mymulticolumn{1}{x{5.377cm}}{number of ways to place k balls in n boxes. \newline % Row Count 1 (+ 1) P = permutation \newline % Row Count 2 (+ 1) C = combination \newline % Row Count 3 (+ 1) Order matters = sequence of choices \newline % Row Count 4 (+ 1) Order doesn't matter = if we picked ball 1 then ball 2… it would be equivalent to picking ball 2 then ball 1 \newline % Row Count 7 (+ 3) With replacement = same item can be picked several times \newline % Row Count 9 (+ 2) Without replacement= each item is chosen at most, 1 time \newline % Row Count 11 (+ 2) {\bf{Case 1}} \newline % Row Count 12 (+ 1) K times out of n objects \newline % Row Count 13 (+ 1) Number of functions from A to B \newline % Row Count 14 (+ 1) |A| = K, |B| = n \newline % Row Count 15 (+ 1) if A has 3 elements, and B has 5… we would get 5\textasciicircum{}3 total functions that can be defined \newline % Row Count 17 (+ 2) {\bf{Case 2}} \newline % Row Count 18 (+ 1) K unique balls in n small boxes (can only fit 1 item in each box) \newline % Row Count 20 (+ 2) number of one to one functions from A to B \newline % Row Count 21 (+ 1) {\bf{Case 3}} \newline % Row Count 22 (+ 1) K identical balls in n small boxes \newline % Row Count 23 (+ 1) Binomial coefficients \newline % Row Count 24 (+ 1) {\bf{Case 4}} \newline % Row Count 25 (+ 1) Bars and stars \newline % Row Count 26 (+ 1) K identical balls in n numbered boxes (but each box can hold \textgreater{}= 0 balls)% Row Count 28 (+ 2) } \tn \hhline{>{\arrayrulecolor{DarkBackground}}-} \end{tabularx} \par\addvspace{1.3em} % That's all folks \end{multicols*} \end{document}