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A357966
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Expansion of e.g.f. exp( x * (exp(x^2) - 1) ).
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3
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1, 0, 0, 6, 0, 60, 360, 840, 20160, 75600, 1058400, 10311840, 79833600, 1305944640, 11018367360, 174616041600, 2150397849600, 28661419987200, 473667677683200, 6293779652160000, 114484773731328000, 1766543101087564800, 31640707215390873600
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) = n! * Sum_{k=0..floor(n/2)} Stirling2(k,n-2*k)/k!.
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PROG
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(PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp(x*(exp(x^2)-1))))
(PARI) a(n) = n!*sum(k=0, n\2, stirling(k, n-2*k, 2)/k!);
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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