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%I #9 Jan 29 2016 11:22:59
%S 441,529,729,841,961,1089,1225,1369,1521,1681,1764,1849,2025,2116,
%T 2209,2401,2601,2809,2916,3025,3249,3364,3481,3721,3844,3969,4225,
%U 4356,4489,4761,4900,5041,5329,5476,5625,5929,6084,6241,6561,6724,6889,7056,7225,7396
%N Squares that can be written as a sum of 3 distinct nonzero squares in 3 or more ways.
%t t = Sort@Select[Flatten[Table[x^2 + y^2 + z^2, {x, 400}, {y, x + 1, 400}, {z, y + 1, 400}]], # < 160006 && IntegerQ[Sqrt[#]] &];
%t 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];
%t f2[l_] := Module[{t = {}}, Do[If[l[[n]] == l[[n + 1]], AppendTo[t, l[[n]]]], {n, Length[l] - 1}]; t];
%t s1 = Join[{First[t]}, f1[t]];
%t Complement[t, s1];
%t t = f2[t];
%t s2 = Join[{First[t]}, f1[t]];
%t Complement[t, s2]
%Y Cf. A161992, A206606, A207638, A207639, A207640.
%K nonn
%O 1,1
%A _Vladimir Joseph Stephan Orlovsky_, Feb 19 2012
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