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Search: id:A113035
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| A113035 |
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Number of ways the set {1,2,...,n} can be split into two subsets of which the sum of one is twice the sum of the other. |
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+0
1
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| 0, 1, 1, 0, 3, 4, 0, 10, 17, 0, 46, 78, 0, 231, 401, 0, 1233, 2177, 0, 6869, 12268, 0, 39502, 71172, 0, 232686, 422076, 0, 1396669, 2547246, 0, 8512170, 15593760, 0, 52534875, 96598865, 0, 327669853, 604405633, 0, 2062171364, 3814087419, 0, 13078921499
(list; graph; listen)
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OFFSET
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1,5
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FORMULA
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a(n) is the coefficient of x^0 in product(x^(-2k)+x^k, k=1..n).
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EXAMPLE
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For n=5 we have 5/1234,14/532 and 23/541 so a(5)=3.
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MAPLE
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A113035:= proc(n) local i, j, p, t; t:= NULL; for j to n do p:=1; for i to j do p:=p*(x^(-2*i)+x^(i)); od; t:=t, coeff(p, x, 0); od; t; end;
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CROSSREFS
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Cf. A058377, A112972.
Sequence in context: A049251 A158674 A056862 this_sequence A099447 A078067 A009126
Adjacent sequences: A113032 A113033 A113034 this_sequence A113036 A113037 A113038
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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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