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 A009276 E..g.f. exp(tanh(x)/exp(x)). 0
 1, 1, -1, -4, 9, 52, -175, -1370, 5985, 60216, -320063, -3929550, 24549745, 354693796, -2543955167, -42233123938, 341610526145, 6404634620016, -57626692351871, -1203767371104790, 11918048043239377, 274395314816604636 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,4 LINKS FORMULA a(n)=sum(m=1..n, sum(i=0..n-m, binomial(n,i+m)*(m^(n-i-m)*(sum(k=0..i+m, stirling2(i+m,k+m)*2^(i-k)*binomial(k+m-1,m-1)*(k+m)!*(-1)^(k+n-i-m)))))/m!), n>0, a(0)=1. [Vladimir Kruchinin, Jun 06 2011] MATHEMATICA Exp[ Tanh[ x ]/Exp[ x ] ] CoefficientList[Series[E^(Tanh[x]/E^x), {x, 0, 20}], x] * Range[0, 20]! (* Vaclav Kotesovec, Jan 23 2015 *) PROG (Maxima) a(n):=sum(sum(binomial(n, i+m)*(m^(n-i-m)*(sum(stirling2(i+m, k+m)*2^(i-k)*binomial(k+m-1, m-1)*(k+m)!*(-1)^(k+n-i-m), k, 0, i+m))), i, 0, n-m)/m!, m, 1, n); [Vladimir Kruchinin, Jun 06 2011] CROSSREFS Sequence in context: A016489 A030694 A060998 * A086692 A242036 A069507 Adjacent sequences:  A009273 A009274 A009275 * A009277 A009278 A009279 KEYWORD sign,easy AUTHOR EXTENSIONS Extended with signs Mar 15 1997 by Olivier Gérard. STATUS approved

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