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A101601 G.f.: c(3x)^3, c(x) the g.f. of A000108. 2

%I

%S 1,9,81,756,7290,72171,729729,7505784,78298974,826489170,8811646074,

%T 94753804536,1026499549140,11192793160815,122744496427425,

%U 1352917116177840,14979996753469110,166542316847391870

%N G.f.: c(3x)^3, c(x) the g.f. of A000108.

%F G.f.: 8/(1+sqrt(1-12*x))^3.

%F a(n) = (3*n+3)/(n+3) * 3^n * C(n+1).

%F Conjecture: (n+3)*a(n) -3*(5*n+7)*a(n-1) +18*(2*n-1)*a(n-2)=0. - _R. J. Mathar_, Nov 15 2011

%t terms = 18;

%t c[x_] = (1 - Sqrt[1 - 4x])/(2x) + O[x]^terms // Normal;

%t CoefficientList[c[3x]^3, x][[1 ;; terms]] (* _Jean-Fran├žois Alcover_, Dec 15 2017 *)

%Y Cf. A050159, A101600, A101602.

%K easy,nonn

%O 0,2

%A _Paul Barry_, Dec 08 2004

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Last modified September 20 10:18 EDT 2021. Contains 347584 sequences. (Running on oeis4.)