The binomial coefficient n choose r.

Given a sequence Q = [r_1, ..., r_k] of positive integers such that n = r_1 + ... + r_k, return the multinomial coefficient n choose r_1, ..., r_k.

The factorial n! for positive small integer n.

The unrestricted partitions of the positive integer n. This function returns a sequence of integer sequences, each of which is a different sequence of positive integers (in descending order) adding up to n. The integer n must be small.

The number of unrestricted partitions of the non-negative integer n. The integer n must be small.

The partitions of the positive integer n, restricted to elements of the positive integer sequence Q.

The Stirling number of the first type, [(m atop n)], where m and n are non-negative integers.

The Stirling number of the second type, {(m atop n)}, where m and n are non-negative integers.

Given an integer n, this function returns the n-th Fibonacci number F_n, which can be defined via the recursion F_0=0, F_1=1 and F_n=F_(n - 1) + F_(n - 2). Note that n is allowed to be negative, and that F_n=( - 1)^(n - 1)F_(-n).