challenge for programmable calculators

[Katie Wasserman]

Code:


%%HP: T(3)A(D)F(.);
\<< 1. 9.
FOR a 1. 9.
FOR b a SQ b * a b SQ * + 1. - NEG DUP SQ a b * 4. * a 100. * b 10. * + * + \v/ + a b * 2. * / DUP FP NOT NOT { DROP } { DUP 10. < { a 100. * b 10. * + + } { DROP } IFTE } IFTE
NEXT
NEXT
\>>

Nice use of the quadratic formula to save the inner-most loop -- compared to the brute force solution. I wonder if there's an even better way.