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 A059386 Expansion of e.g.f. cosh(cosh(x)-1) (even powers only). 2
 1, 0, 3, 15, 168, 3405, 77253, 2151240, 77493783, 3369709995, 169438618608, 9847267355145, 658888820876553, 49985438650733040, 4245160431876404043, 401030532597501719655, 41924382309752516224728, 4820179120197824593864965 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS a(n) is the number of partitions of the set {1, 2, ..., 2n} into an even number of blocks, each containing an even number of elements. - Isabel C. Lugo (izzycat(AT)gmail.com), Aug 23 2004 REFERENCES L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 226, 9th line of table. LINKS G. C. Greubel, Table of n, a(n) for n = 0..250 MAPLE seq(factorial(k)*coeftayl(cosh(cosh(x)-1), x = 0, k), k=0..200, 2); # Muniru A Asiru, Jan 29 2018 MATHEMATICA nn = 30; Insert[Select[Range[0, nn]! CoefficientList[Series[Cosh[Cosh[x] - 1], {x, 0, nn}], x], # > 0 &], 0, 2] (* Geoffrey Critzer, Mar 31 2012 *) With[{nn = 50}, CoefficientList[Series[Cosh[Cosh[x] - 1], {x, 0, nn}], x] Range[0, nn]!][[1 ;; ;; 2]] (* G. C. Greubel, Jan 29 2018 *) PROG (PARI) x='x+O('x^50); v=Vec(serlaplace(cosh(cosh(x)-1))); vector(#v\2, n, v[2*n-1]) \\ G. C. Greubel, Jan 29 2018 CROSSREFS Sequence in context: A269694 A153280 A132683 * A077792 A153079 A173301 Adjacent sequences:  A059383 A059384 A059385 * A059387 A059388 A059389 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 28 2001 STATUS approved

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Last modified January 22 10:25 EST 2020. Contains 331144 sequences. (Running on oeis4.)