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 A255927 a(n) = (3/4) * Sum_{k>=0} (3*k)^n/4^k. 1
 1, 1, 5, 33, 285, 3081, 40005, 606033, 10491885, 204343641, 4422082005, 105265315233, 2733583519485, 76902684021801, 2329889536156005, 75629701786875633, 2618654297178083085, 96336948993312237561, 3752590641305604502005, 154294551397830418471233, 6677999524135208461382685 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Alois P. Heinz, Table of n, a(n) for n = 0..400 P. Blasiak, K. A. Penson and A. I. Solomon, Dobinski-type relations and the Log-normal distribution, arXiv:quant-ph/0303030, 2003. P. Blasiak, K. A. Penson and A. I. Solomon, Dobinski-type relations and the Log-normal distribution, J. Phys. A: Math. Gen. 36, (2003), L273. Eric Weisstein's MathWorld, Lerch Transcendent FORMULA a(n) = Sum_{k>=0} Stirling2(n,k)*k!*3^(n-k). E.g.f.: 3/(4-exp(3*x)). Special values of the generalized hypergeometric function n_F_(n-1): a(n) = (3^(n+1)/16) * hypergeom([2,2,..2],[1,1,..1],1/4), where the sequence in the first square bracket ("upper" parameters) has n elements all equal to 2 whereas the sequence in the second square bracket ("lower" parameters) has n-1 elements all equal to 1. Example: a(5) = 729 * hypergeom([2,2,2,2,2],[1,1,1,1],1/4)/16 = 3081. a(n) is the n-th moment of the discrete weight function W(x) = (3/4)*sum(k>=0, Dirac(x-3*k)/4^k), n>=1. a(n) ~ n! * 3^(n+1) / ((log(2))^(n+1) * 2^(n+3)). - Vaclav Kotesovec, Jul 09 2018 G.f.: Sum_{j>=0} j!*x^j / Product_{k=1..j} (1 - 3*k*x). - Ilya Gutkovskiy, Apr 04 2019 EXAMPLE a(5) = 729*hypergeom([2,2,2,2,2],[1,1,1,1],1/4)/16 = 3081. MAPLE S:= series(3/(4-exp(3*x)), x, 51): seq(coeff(S, x, n)*n!, n=0..50); # Robert Israel, Sep 03 2015 MATHEMATICA a[n_] := 3^(n+1)/4 HurwitzLerchPhi[1/4, -n, 0]; Table[a[n], {n, 0, 20}] (* Jean-François Alcover, Sep 18 2018 *) PROG (PARI) a(n) = sum(k=0, n, stirling(n, k, 2)*k!*3^(n-k)); \\ Michel Marcus, Sep 03 2015 CROSSREFS Cf. A000670, A094418, A004123 A032033, A094417, A122704. Sequence in context: A218496 A144792 A291846 * A001828 A084845 A198079 Adjacent sequences:  A255924 A255925 A255926 * A255928 A255929 A255930 KEYWORD nonn,changed AUTHOR Karol A. Penson, Sep 03 2015 EXTENSIONS a(0)=1 prepended by Alois P. Heinz, Sep 18 2018 STATUS approved

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Last modified April 18 16:45 EDT 2019. Contains 322209 sequences. (Running on oeis4.)