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A009257
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E.g.f. exp(tanh(log(1+x))).
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0
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1, 1, 0, -2, 4, 6, -74, 190, 1128, -14336, 51616, 404856, -7330520, 41023048, 250083744, -7532037344, 65189204416, 185746926720, -13324842809792, 175157684686144, -215786634724224, -35458746254274944, 711274631768613760
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,4
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FORMULA
| a(n)=sum(m=1..n, sum(r=0..n-m, stirling1(n,r+m)*sum(k=0..r, binomial(k+m-1,m-1)*(k+m)!*(-1)^(k)*2^(r-k)*stirling2(r+m,k+m)))/m!), n>0, a(0)=1. [From Vladimir Kruchinin, Jun 06 2011]
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MATHEMATICA
| Exp[ Tanh[ Log[ 1+x ] ] ]
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PROG
| (Maxima)
a(n):=sum(sum(stirling1(n, r+m)*sum(binomial(k+m-1, m-1)*(k+m)!*(-1)^(k)*2^(r-k)*stirling2(r+m, k+m), k, 0, r), r, 0, n-m)/m!, m, 1, n); [From Vladimir Kruchinin, Jun 06 2011]
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CROSSREFS
| Sequence in context: A173818 A084324 A066220 * A098757 A056012 A066719
Adjacent sequences: A009254 A009255 A009256 * A009258 A009259 A009260
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KEYWORD
| sign,easy
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AUTHOR
| R. H. Hardin (rhhardin(AT)att.net)
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EXTENSIONS
| Extended with signs Mar 15 1997 by Olivier Gerard.
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