OFFSET
1,1
MATHEMATICA
Su[n_] := Su[n] = Mod[Sum[GCD[i, n]*PowerMod[i, n, n], {i, 1, n}], n]; Select[Range[400], ! Su[2#] == # &]
CROSSREFS
KEYWORD
nonn
AUTHOR
José María Grau Ribas, Feb 01 2014
STATUS
approved