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Search: id:A113036
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| A113036 |
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Number of solutions to +- 1 +- 2 +- .. +- n = 2. |
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+0
1
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| 0, 0, 1, 2, 0, 0, 8, 13, 0, 0, 69, 123, 0, 0, 719, 1313, 0, 0, 8215, 15260, 0, 0, 99774, 187615, 0, 0, 1264854, 2399207, 0, 0, 16544234, 31587644, 0, 0, 221625505, 425313967, 0, 0, 3025271756, 5829531261, 0, 0, 41929052284, 81066732018, 0
(list; graph; listen)
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OFFSET
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1,4
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FORMULA
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a(n) is the coefficient of x^2 in product(x^(-k)+x^k, k=1..n).
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MAPLE
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A113036:= proc(n) local i, j, p, t; t:= NULL; for j to n do p:=1; for i to j do p:=p*(x^(-i)+x^i); od; t:=t, coeff(p, x, 2); od; t; end;
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CROSSREFS
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Cf. A058377, A063865, A063866.
Sequence in context: A058347 A058547 A134414 this_sequence A000425 A010893 A000171
Adjacent sequences: A113033 A113034 A113035 this_sequence A113037 A113038 A113039
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KEYWORD
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nonn
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AUTHOR
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Floor van Lamoen (fvlamoen(AT)hotmail.com),Oct 11 2005
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