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 A188687 Partial binomial sums of binomial(3n,n)/(2n+1) = A001764(n). 11
 1, 2, 6, 25, 126, 704, 4183, 25897, 165166, 1077520, 7156352, 48222354, 328859011, 2265428728, 15740837575, 110187356134, 776336572878, 5501042194580, 39177463572112, 280277949384146, 2013277273220064, 14514764553512488, 104993261648226446 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Nathaniel Johnston, Table of n, a(n) for n = 0..400 FORMULA a(n) = sum(binomial(n,k)*binomial(3k,k)/(2k+1),k=0..n). G.f.: (2/sqrt(3x*(1-x)))*sin((1/3)*arcsin(3/2*sqrt(3*x/(1-x)))). Recurrence: 2*n*(2*n+1)*a(n) = (39*n^2-35*n+8)*a(n-1) - 2*(n-1)*(33*n-32)*a(n-2) + 31*(n-2)*(n-1)*a(n-3). - Vaclav Kotesovec, Oct 20 2012 a(n) ~ 31^(n+3/2)/(3^4*2^(2*n+2)*sqrt(Pi)*n^(3/2)). - Vaclav Kotesovec, Oct 20 2012 MATHEMATICA Table[Sum[Binomial[n, k]Binomial[3k, k]/(2k+1), {k, 0, n}], {n, 0, 22}] PROG (Maxima) makelist(sum(binomial(n, k)*binomial(3*k, k)/(2*k+1), k, 0, n), n, 0, 20); CROSSREFS Cf. A005809, A001764, A188675, A188676, A104859, A188678, A188679, A188680, A188681, A188682, A188683, A188684, A188685, A188686. Sequence in context: A030828 A030839 A030851 * A030859 A030877 A275754 Adjacent sequences:  A188684 A188685 A188686 * A188688 A188689 A188690 KEYWORD nonn,easy AUTHOR Emanuele Munarini, Apr 08 2011 STATUS approved

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Last modified January 20 14:40 EST 2019. Contains 319333 sequences. (Running on oeis4.)