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 A053488 E.g.f.: exp(exp(sinh(x))-1)-1. 1
 0, 1, 2, 6, 23, 103, 535, 3153, 20676, 149148, 1172343, 9960085, 90864801, 885278605, 9167936406, 100508961982, 1162366436355, 14136151459043, 180287711599455, 2405321659729837, 33495442060505752, 485880832780748932 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS a(n) is the number of pairs (d,d') of set partitions of {1,2,...,n} such that d is finer than d' and all block sizes of d are odd. - Geoffrey Critzer, Dec 28 2011 REFERENCES R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Example 5.1.14. LINKS G. C. Greubel, Table of n, a(n) for n = 0..400 Vladimir Kruchinin, D. V. Kruchinin, Composita and their properties, arXiv:1103.2582 [math.CO], 2011. FORMULA a(n) = Sum_{m=1..n} ( Sum_{k} 1/(2^k*k!)*Sum_{i=0..k} (-1)^i*binomial(k,i)*(k-2*i)^n)*stirling2(k,m),k,m,n)), n>0. - Vladimir Kruchinin, Sep 10 2010 MATHEMATICA nn = 21; a = Sinh[x]; Range[0, nn]! CoefficientList[Series[Exp[Exp[a] - 1] - 1, {x, 0, nn}], x]  (* Geoffrey Critzer, Dec 28 2011 *) PROG (Maxima) a(n):=sum(sum(1/(2^k*k!)*sum((-1)^i*binomial(k, i)*(k-2*i)^n, i, 0, k)*stirling2(k, m), k, m, n), m, 1, n);  /* Vladimir Kruchinin, Sep 10 2010 */ CROSSREFS Sequence in context: A005802 A061552 A263778 * A117106 A137534 A137535 Adjacent sequences:  A053485 A053486 A053487 * A053489 A053490 A053491 KEYWORD nonn AUTHOR N. J. A. Sloane, Jan 15 2000 STATUS approved

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Last modified November 18 17:49 EST 2018. Contains 317323 sequences. (Running on oeis4.)