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 A009733 Expansion of tan(x)*cosh(tan(x)). 0
 1, 5, 81, 2477, 120481, 8496245, 817734321, 102873611549, 16372688411713, 3213260867586149, 761792907575450385, 214507625428065409805, 70732793117238811066081, 26987583518243293948764629 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS FORMULA 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 MATHEMATICA 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 *) PROG (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 */ CROSSREFS Sequence in context: A115032 A278883 A307376 * A009756 A336807 A188419 Adjacent sequences: A009730 A009731 A009732 * A009734 A009735 A009736 KEYWORD nonn AUTHOR EXTENSIONS Extended and signs tested by Olivier Gérard, Mar 15 1997 Prior Mathematica program replaced by Harvey P. Dale, Jan 14 2015 STATUS approved

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Last modified February 1 08:20 EST 2023. Contains 359992 sequences. (Running on oeis4.)