OFFSET
1,1
MATHEMATICA
fu[n_] := fu[n] = Mod[Sum[PowerMod[i + j I, n, n], {i, 0, n - 1}, {j, 0, n - 1}], n]; Table[If[! fu[24(3n - 1)]/(3n - 1) == 16, Print[n]; n], {n, 1, 40}]
CROSSREFS
KEYWORD
nonn,more,hard
AUTHOR
José María Grau Ribas, Nov 17 2013
STATUS
approved