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A009733
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Expansion of tan(x)*cosh(tan(x)).
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0
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1, 5, 81, 2477, 120481, 8496245, 817734321, 102873611549, 16372688411713, 3213260867586149, 761792907575450385, 214507625428065409805, 70732793117238811066081, 26987583518243293948764629
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = b(2*n-1), b(n) = Sum_{k=1..n} ((-1)^(k-1)+1)/(k-1)!*((-1)^(n-k)+1)*Sum_{j=k..n} binomial(j-1,k-1)*j!*2^(n-j-2)*(-1)^((n+k)/2+j)*stirling2(n,j). - Vladimir Kruchinin, Apr 21 2011
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MATHEMATICA
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With[{nn=30}, Take[CoefficientList[Series[Tan[x]Cosh[Tan[x]], {x, 0, nn}], x] Range[0, nn-1]!, {2, -1, 2}]] (* Harvey P. Dale, Jan 14 2015 *)
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PROG
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(Maxima)
a(n):=b(2*n-1);
b(n):=sum(((-1)^(k-1)+1)/(k-1)!*((-1)^(n-k)+1)*sum(binomial(j-1, k-1)*j!*2^(n-j-2)*(-1)^((n+k)/2+j)*stirling2(n, j), j, k, n), k, 1, n); /* Vladimir Kruchinin, Apr 21 2011 */
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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