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A009672
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Expansion of e.g.f. tan(sin(x)*exp(x)).
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0
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0, 1, 2, 4, 24, 172, 1192, 10176, 106176, 1212048, 15123872, 210069440, 3195595392, 52434870464, 926003117184, 17548224583168, 354716499392512, 7614573123195136, 173087393243492864, 4153672167748662272
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OFFSET
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0,3
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LINKS
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FORMULA
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a(n) = 2*sum(k=0..(n-1)/2, ((sum(j=1..2*k+1, j!*2^(-j)*(-1)^(j)*stirling2(2*k+1,j)))*sum(r=k..(n-1)/2, binomial(n,n-1-2*r)*((2*k+1)^(n-1-2*r)*sum(i=0..(2*k+1)/2, (2*i-2*k-1)^(2*r+1)*binomial(2*k+1,i)*(-1)^(r-i)))))/(2*k+1)!). - Vladimir Kruchinin, Jun 13 2011
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MATHEMATICA
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With[{nn=20}, CoefficientList[Series[Tan[Sin[x]Exp[x]], {x, 0, nn}], x] Range[ 0, nn]!] (* Harvey P. Dale, Jul 31 2018 *)
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PROG
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(Maxima)
a(n):=2*sum(((sum(j!*2^(-j)*(-1)^(j)*stirling2(2*k+1, j), j, 1, 2*k+1))*sum(binomial(n, n-1-2*r)*((2*k+1)^(n-1-2*r)*sum((2*i-2*k-1)^(2*r+1)*binomial(2*k+1, i)*(-1)^(r-i), i, 0, (2*k+1)/2)), r, k, (n-1)/2))/(2*k+1)!, k, 0, (n-1)/2); /* Vladimir Kruchinin, Jun 13 2011 */
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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