Permutation and Combination
permutation
${}_n \mathrm{ P }_k$
{}_n \mathrm{ P }_k
To write a small letter in the lower left corner, use "{}_". "P" is Roman type.
combination
${}_n \mathrm{ C }_k$
{}_n \mathrm{ C }_k
factorial
$n!$
n!
binomial coefficient
$\binom{ n }{ k }$
\binom{ n }{ k }
\binom comes from "binomial coefficient".係数)に由来しています。
binomial coefficient 2
${ n \choose k }$
{ n \choose k }
\choose is used to choose k from n. The braces are necessary to separate it from the preceding and following characters.
binomial coefficient 3
$\dbinom{ n }{ k }$
\dbinom{ n }{ k }
This is \binom in displaystyle.
repeated combination
${}_n \mathrm{ H }_k$
{}_n \mathrm{ H }_k
combination sample
$\begin{eqnarray} {}_n \mathrm{ C }_k = \binom{ n }{ k } = \frac{ n! }{ k! ( n - k )! } \end{eqnarray}$
\begin{eqnarray} {}_n \mathrm{ C }_k = \binom{ n }{ k } = \frac{ n! }{ k! ( n - k )! } \end{eqnarray}
permutation sample
$\begin{eqnarray} {}_n \mathrm{ P }_k = n \cdot ( n - 1 ) \cdots ( n - k + 1 ) = \frac{ n! }{ ( n - k )! } \end{eqnarray}$
\begin{eqnarray} {}_n \mathrm{ P }_k = n \cdot ( n - 1 ) \cdots ( n - k + 1 ) = \frac{ n! }{ ( n - k )! } \end{eqnarray}