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A188898
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The index of the least n-gonal number greater than 1 that is also square, or 0 if none exists.
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2
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8, 2, 81, 25, 6, 9, 2, 0, 7, 4, 3, 9, 22, 2, 49, 4, 8, 0, 17, 9, 81, 5, 2, 25, 46, 3, 10, 121, 6, 9, 18, 4, 31, 2, 11, 169, 7, 6, 1681, 49, 8, 4, 4961, 12, 225, 8, 2, 16, 32, 0, 49, 25, 17, 13, 289, 9, 49, 7, 27, 81, 118, 2, 136161, 196, 14, 4, 10, 841, 1521
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OFFSET
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3,1
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COMMENTS
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Sequence A188896 gives the n that have no solution.
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LINKS
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Table of n, a(n) for n=3..71.
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FORMULA
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If n is a square, then a(n)=2.
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MATHEMATICA
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kMax = 25000; NgonIndex[n_, v_] := (-4 + n + Sqrt[16 - 8*n + n^2 - 16*v + 8*n*v])/(n - 2)/2; Table[k = 2; While[sqr = k^2; i = NgonIndex[n, sqr]; k < kMax && ! IntegerQ[i], k++]; If[k == kMax, k = sqr = i = 0]; i, {n, 3, 64}]
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CROSSREFS
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Cf. A100252 (least square n-gonal number greater than 1).
Sequence in context: A202625 A038280 A032761 * A176860 A093082 A107671
Adjacent sequences: A188895 A188896 A188897 * A188899 A188900 A188901
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe, Apr 13 2011
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STATUS
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approved
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