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

1,1

Links

Table of n, a(n) for n=1..44.

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]

Crossrefs

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

Sequence in context: A272716 A124170 A252193 * A207045 A252201 A252194

Adjacent sequences: A207647 A207648 A207649 * A207651 A207652 A207653

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Feb 19 2012

Status

approved