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A134531
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G.f.: Sum_{n>=0} a(n)*x^n/(n!*2^(n*(n-1)/2)) = log( Sum_{n>=0} x^n/(n!*2^(n*(n-1)/2)) ).
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11
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0, 1, -1, 5, -79, 3377, -362431, 93473345, -56272471039, 77442176448257, -239804482525402111, 1650172344732021412865, -24981899010711376986398719, 825164608171793476724052668417, -59053816996641612758331731690504191, 9102696765174239045811746247171452452865
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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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Equals column 0 of triangle A134530, which is the matrix log of triangle A111636, where A111636(n,k) = (2^k)^(n-k)*C(n,k).
Let E(x) = Sum_{n >= 0} x^n/(n!*2^C(n,2)). Then a generating function for this sequence (but with a different offset) is E(x)/E(2*x) = Sum_{n >= 0} a(n-1)*x^n/(n!*2^C(n,2)) = 1 - x + 5*x^2/(2!*2) - 79*x^3/(3!*2^3) + 3377*x^4/(4!*2^6) - ....
Recurrence equation:
a(n) = 1 - Sum_{k = 1..n-1} 2^(k*(n-k))*C(n-1,k-1)*a(k) with a(1) = 1. (End)
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EXAMPLE
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Let g.f. G(x) = Sum_{n>=0} a(n)*x^n/[ n! * 2^(n*(n-1)/2) ]
then exp(G(x)) = Sum_{n>=0} x^n/[ n! * 2^(n*(n-1)/2) ];
G.f.: G(x) = x - x^2/4 + 5x^3/48 - 79x^4/1536 + 3377x^5/122880 + ...
exp(G(x)) = 1 + x + x^2/4 + x^3/48 + x^4/1536 + x^5/122880 + ...
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MATHEMATICA
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a[0] = 0;
a[n_] := a[n] = 1 - Sum[2^(k(n-k)) Binomial[n-1, k-1] a[k], {k, 1, n-1}];
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PROG
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(PARI) {a(n)=n!*2^(n*(n-1)/2)*polcoeff(log(sum(k=0, n, x^k/(k!*2^(k*(k-1)/2)))+x*O(x^n)), n)}
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CROSSREFS
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KEYWORD
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sign,easy
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AUTHOR
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STATUS
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approved
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