HP 50g Programming Competition: How Many Partitions of an Integer in 4 Squares

[Thomas Ritschel]

I've got it further improved and significantly smaller:

Code:

%%HP: T(3)A(R)F(.);
@ Jacobi, by Thomas Ritschel
@ number of representations
@ Jacobi's four-square theorem
@ idea based on Joe Horn's \Gs
\<< FACTORS DUP SIZE
  IF 0 >
  THEN R\->I OBJ\-> 1 SWAP 1. SWAP 2. /
    START PICK3 DUP
      IF 2 ==
      THEN ROT DROP 1 UNROT
      END ROT 1 + ^ 1 - ROT 1 - / *
    NEXT
  ELSE DROP 1
  END 8 *
\>>

Runtime for 720^20 and '720^20' is slightly slower: 0.69 and 0.72 secs, respectively.