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A113037
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Number of solutions to +- 1 +- 2 +- .. +- n = 3.
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1
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0, 1, 0, 0, 3, 5, 0, 0, 23, 39, 0, 0, 219, 396, 0, 0, 2406, 4435, 0, 0, 28431, 53167, 0, 0, 353500, 667874, 0, 0, 4557831, 8675836, 0, 0, 60382450, 115601178, 0, 0, 816998489, 1571272955, 0, 0, 11242173783, 21701318843, 0, 0, 156841667096
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,5
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FORMULA
| a(n) is the coefficient of x^3 in product(x^(-k)+x^k, k=1..n).
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MAPLE
| A113037:= 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, 3); od; t; end;
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CROSSREFS
| Cf. A058377, A063865, A063866.
Sequence in context: A152624 A059107 A025115 * A063866 A059106 A087676
Adjacent sequences: A113034 A113035 A113036 * A113038 A113039 A113040
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KEYWORD
| nonn
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AUTHOR
| Floor van Lamoen (fvlamoen(AT)hotmail.com),Oct 11 2005
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