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A009256
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E.g.f. exp(tan(x)^2) (even powers only).
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0
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1, 2, 28, 872, 47248, 3907232, 454886848, 70597546112, 14042505449728, 3475021574246912, 1045247734061145088, 375054668796817221632, 158085597663328138006528, 77269840864693331267919872
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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FORMULA
| a(n)=sum(k=1..n, (sum(j=2*k..2*n, binomial(j-1,2*k-1)*j!*2^(2*n-j)*(-1)^(n+k+j)*stirling2(2*n,j)))/k!); [From Vladimir Kruchinin, Jun 06 2011]
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MATHEMATICA
| Exp[ Tan[ x ]^2 ] (* Even Part *)
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PROG
| (Maxima)
a(n):=sum((sum(binomial(j-1, 2*k-1)*j!*2^(2*n-j)*(-1)^(n+k+j)*stirling2(2*n, j), j, 2*k, 2*n))/k!, k, 1, n); [From Vladimir Kruchinin, Jun 06 2011]
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CROSSREFS
| Sequence in context: A098631 A089836 A090249 * A012725 A012756 A009403
Adjacent sequences: A009253 A009254 A009255 * A009257 A009258 A009259
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KEYWORD
| nonn
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AUTHOR
| R. H. Hardin (rhhardin(AT)att.net)
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EXTENSIONS
| Extended and signs tested Mar 15 1997 by Olivier Gerard.
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