Let's define a factorial-like function, and for lack of a better name let's denote it x?:

x? = 1 * 1.5 * 2 * 2.5 * 3 * 3.5 * ... * (n - 0.5) * n

Thus,

2? = 1 * 1.5 * 2 = 33.5? = 1 * 1.5 * 2 * 2.5 * 3 * 3.5 = 78.75

Write a small program to compute this function on your HP calculator of choice. Smallest programs win (least size in bytes or number of steps) for each calculator. RPN programs should not destroy register X. So far I have a 9-step program for the 12C and most scientific RPN calculators (LBL and RTN and final GTO 00 don't count) and a 16.5-byte program for the 32SII, but I hope you can improve this. Searching through the internet for reference is allowed and encouraged.

The function can be generalized for real arguments other than those ending in 0.5. So,

3.333333? = 51.0575911879(2 * pi)? = 668840.9993

80(bold digits not correct)

(the HP-12C program will not handle these).

Gerson.