HP 40G manual Probability functions, Comb, Perm, Random

H I N T	The results of POLYROOT will often not be easily seen in
	HOME due to the number of decimal places, especially if they
	are complex numbers. It is better to store the results of
	POLYROOT to a matrix.
	For example, POLYROOT([1,0,0,-8]672?_￿M1 will store
	the three complex cube roots of 8 to matrix M1 as a complex
	vector. Then you can see them easily by going to the Matrix
	Catalog. and access them individually in calculations by
	referring to M1(1), M1(2) etc.
Probability functions
COMB	Number of combinations (without regard to order) of n things
	taken r at a time: n!/(r!(n−r)).
	COMB(n,r)
	Example
	COMB(5,2) returns 10. That is, there are ten different
	ways that five things can be combined two at a time.
!	Factorial of a positive integer. For non-integers, ! = Γ(x + 1).
	This calculates the gamma function.
	value!
PERM	Number of permutations (with regard to order) of n things
	taken r at a time: n!/ (n-r)!.
	PERM (n,r)
	Example
	PERM(5,2) returns 20. That is, there are 20 different
	permutations of five things taken two at a time.
RANDOM	Random number (between zero and 1). Produced by a pseudo-
	random number sequence. The algorithm used in the
	RANDOM function uses a “seed” number to begin its
	sequence. To ensure that two calculators must produce

different results for the RANDOM function, use the RANDSEED function to seed different starting values before using RANDOM to produce the numbers.

RANDOM

Using mathematical functions 10-13