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 A009273 E.g.f. exp(x*tanh(x)) (even powers only). 4
 1, 2, 4, -24, 400, -5600, -103872, 26975872, -3438685952, 417995260416, -51382607559680, 5994623640856576, -454930757753597952, -94991612229069430784, 81515752167646959124480 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA a(n)=sum(m=0..2*n, binomial(2*n,m)*sum(k=0..2*n-2*m, binomial(k+m-1,m-1)*(k+m)!*(-1)^(k)*2^(2*n-2*m-k)*stirling2(2*n-m,k+m))), n>0, a(0)=1. - Vladimir Kruchinin, Jun 06 2011 MATHEMATICA Exp[ Tanh[ x ]*x ] (* Even Part *) PROG (Maxima) a(n):=sum(binomial(2*n, m)*sum(binomial(k+m-1, m-1)*(k+m)!*(-1)^(k)*2^(2*n-2*m-k)*stirling2(2*n-m, k+m), k, 0, 2*n-2*m), m, 0, 2*n); /* Vladimir Kruchinin, Jun 06 2011 */ CROSSREFS Sequence in context: A030276 A081476 A241806 * A332539 A296787 A341633 Adjacent sequences:  A009270 A009271 A009272 * A009274 A009275 A009276 KEYWORD sign AUTHOR EXTENSIONS Extended with signs by Olivier Gérard, Mar 15 1997 STATUS approved

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Last modified July 31 12:29 EDT 2021. Contains 346373 sequences. (Running on oeis4.)