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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

Table of n, a(n) for n=0..21.

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

R. H. Hardin

EXTENSIONS

Extended with signs Mar 15 1997 by Olivier Gérard.

STATUS

approved

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Last modified August 29 08:06 EDT 2015. Contains 261188 sequences.