Most mind-blowing program for your favorite calculator

[xerxes]

The HP-25 solution of N-queens is one of my favorites. Very impressive.

The most challenging program on my very first programmable calculator, the FX-180P, was the Collatz conjecture. First I thought, that it's not possible to write a program
for the output of the number of interations and the maximum. But after some effort I managed to do it.

Code:

 01  2
 02  Kin/1
 03  Kout1
 04  -
 05  1
 06  Kin+3
 07  =
 08  1/x
 09  Kout1
 10  Kin2
 11  FIX0
 12  RND
 13  NORM
 14  Kin-2
 15  .
 16  5
 17  Kin+2
 18  Kout2
 19  x>0
 20  6
 21  Kin*1
 22  1
 23  Kin+1
 24  Kout1
 25  x<=M
 26  Min
 27  RTN


Usage example:

KAC Min 27 Kin1 P1

program stops with error

Kout3 -> 111

MR -> 9232