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A025321
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Numbers that are the sum of 3 nonzero squares in exactly 1 way.
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7
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3, 6, 9, 11, 12, 14, 17, 18, 19, 21, 22, 24, 26, 29, 30, 34, 35, 36, 42, 43, 44, 45, 46, 48, 49, 50, 53, 56, 61, 65, 67, 68, 70, 72, 73, 76, 78, 82, 84, 88, 91, 93, 96, 97, 104, 106, 109, 115, 116, 120, 133, 136, 140, 142, 144, 145, 157, 163, 168, 169, 172, 176, 180, 184, 190
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OFFSET
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1,1
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COMMENTS
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It appears that all terms have the form 4^i A094740(j) for some i and j. - T. D. Noe, Jun 06 2008
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LINKS
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FORMULA
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MATHEMATICA
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lim=20; nLst=Table[0, {lim^2}]; Do[n=a^2+b^2+c^2; If[n>0 && n<lim^2, nLst[[n]]++ ], {a, lim}, {b, a, Sqrt[lim^2-a^2]}, {c, b, Sqrt[lim^2-a^2-b^2]}]; Flatten[Position[nLst, 1]] (* T. D. Noe, Jun 06 2008 *)
b[n_, i_, k_, t_] := b[n, i, k, t] = If[n == 0, If[t == 0, 1, 0], If[i<1 || t<1, 0, b[n, i - 1, k, t] + If[i^2 > n, 0, b[n - i^2, i, k, t - 1]]]];
T[n_, k_] := b[n, Sqrt[n] // Floor, k, k];
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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