fallingfactorial: Computes the falling factorial.

In aschleg/numberr: Numberr is a package containing number-theoretic algorithms and functions primarily written in C++ using Rcpp

Description

The falling factorial, denoted as (x)_{n} (or x^{\underline{n}}) is defined as the following:

(x)_n = x(x - 1) \cdots (x - (n - 1))

The first few falling factorials are then:

(x)_0 = 1

(x)_1 = x

(x)_2 = x(x - 1)

(x)_3 = x(x - 1)(x - 2)

(x)_4 = x(x - 1)(x - 2)(x - 3)

Usage

fallingfactorial(x, n)

Arguments

x	integer
n	integer

Value

Computed falling factorial

References

Falling and rising factorials. (2017, June 8). In Wikipedia, The Free Encyclopedia. From https://en.wikipedia.org/w/index.php?title=Falling_and_rising_factorials&oldid=784512036 Weisstein, Eric W. "Falling Factorial." From MathWorld–A Wolfram Web Resource. http://mathworld.wolfram.com/FallingFactorial.html

Examples

fallingfactorial(5, 3)
fallingfactorial(10, 6)

aschleg/numberr documentation built on May 14, 2019, 10:31 a.m.