OFFSET
0,1
PROG
(PARI) issum2sq(n) = local(fm, hf); hf=0; fm=factor(n); for(i=1, matsize(fm)[1], if(fm[i, 1]==2, if(fm[i, 2]%2, hf=1), if(fm[i, 1]%4==1, hf=1, if(fm[i, 2]%2, return(0))))); hf
minsum2sq(n) = local(k); k=1; while(!issum2sq(k^2-n), k++); k
/* Note: the issum2sq function depends on PARI returning -1 as a factor for negative n. */
CROSSREFS
KEYWORD
nonn
AUTHOR
Franklin T. Adams-Watters, Apr 26 2009
STATUS
approved