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A363817
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G.f. satisfies A(x) = (1 + x/A(x))/(1 - x)^3.
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1
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1, 4, 5, 15, -5, 111, -402, 2172, -10892, 57362, -305756, 1656560, -9083341, 50328219, -281324174, 1584578882, -8984740332, 51242962422, -293772467974, 1691974930794, -9785378133066, 56805049768410, -330880419984556, 1933299689139664, -11328101469158229
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OFFSET
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0,2
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LINKS
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FORMULA
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G.f.: A(x) = -2*x / (1-sqrt(1+4*x*(1-x)^3)).
a(n) = (-1)^(n-1) * Sum_{k=0..n} binomial(2*k-1,k) * binomial(3*(k-1),n-k)/(2*k-1).
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PROG
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(PARI) a(n) = (-1)^(n-1)*sum(k=0, n, binomial(2*k-1, k)*binomial(3*(k-1), n-k)/(2*k-1));
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CROSSREFS
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KEYWORD
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sign
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AUTHOR
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STATUS
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approved
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