HP 33s - Manual (Page 78)

4–14 Real–Number Functions
Probability Functions
Factorial
To calculate the factorial of a displayed non-negative integer x (0 ≤ x ≤ 253), press
{ (the left–shifted key).
Gamma
To calculate the gamma function of a noninteger x, Γ(x), key in (x – 1) and press
{ . The x! function calculates Γ(x + 1). The value for x cannot be a negative
integer.
Probability
Combinations
To calculate the number of possible sets of n items taken r at a time, enter n first,
{ \ , then r (nonnegative integers only). No item occurs more than once in a
set, and different orders of the same r items are not counted separately.
Permutations
To calculate the number of possible arrangements of n items taken r at a time, enter
n
first, { _ , then r (nonnegative integers only). No item occurs more than
once in an arrangement, and different orders of the same r items are counted
separately.
Seed
To store the number in x as a new seed for the random number generator, press
| i .
Random number generator
To generate a random number in the range 0 ≤ x < 1, press | k . (The
number is part of a uniformly–distributed pseudo–random number sequence. It
passes the spectral test of D. Knuth, The Art of Computer Programming, vol. 2,
Seminumerical Algorithms
, London: Addison Wesley, 1981.)