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Adapted to the HP-42S by Richard
Garner This program calculates approximations for big factorials (N!
for N > 253) on the HP-42S. This program was originally written for
the 41C and published in the PPC Journal.
Usage:
Enter a non-negative integer and run BN!. The result is returned in Y
(the mantissa) and X (the exponent) and is also shown in the alpha
register.
Example:
Technical notes:
For N < 254 the built-in N! function is called.
The precision of the approximation goes down for very large N.
All seven digits of the multiplier are correct for N<10 000, for N =
100 000 five digits are correct and for N = 1 000 000 three digits are
correct.