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A207650 Squares that can be written as a sum of 3 distinct nonzero squares in 3 or more ways. 0
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 23 20:42 EDT 2021. Contains 347617 sequences. (Running on oeis4.)