A207650 Squares that can be written as a sum of 3 distinct nonzero squares in 3 or more ways.

441, 529, 729, 841, 961, 1089, 1225, 1369, 1521, 1681, 1764, 1849, 2025, 2116, 2209, 2401, 2601, 2809, 2916, 3025, 3249, 3364, 3481, 3721, 3844, 3969, 4225, 4356, 4489, 4761, 4900, 5041, 5329, 5476, 5625, 5929, 6084, 6241, 6561, 6724, 6889, 7056, 7225, 7396

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Feb 19 2012

Keywords

• nonn

Crossrefs

Cf. A161992, A206606, A207638, A207639, A207640.

Programs

Mathematica

t = Sort@Select[Flatten[Table[x^2 + y^2 + z^2, {x, 400}, {y, x + 1, 400}, {z, y + 1, 400}]], # < 160006 && IntegerQ[Sqrt[#]] &];
f1[l_] := Module[{t = {}}, Do[If[l[[n]] != l[[n + 1]] && l[[n]] != l[[n - 1]], AppendTo[t, l[[n]]]], {n, Length[l] - 1}]; t];
f2[l_] := Module[{t = {}}, Do[If[l[[n]] == l[[n + 1]], AppendTo[t, l[[n]]]], {n, Length[l] - 1}]; t];
s1 = Join[{First[t]}, f1[t]];
Complement[t, s1];
t = f2[t];
s2 = Join[{First[t]}, f1[t]];
Complement[t, s2]