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A130579 Convolution of A000108 (Catalan numbers) and A001764 (ternary trees): a(n) = Sum_{k=0..n} C(2k,k) * C(3(n-k),n-k) / [(k+1)(2(n-k)+1)]. 0
1, 2, 6, 22, 92, 423, 2087, 10856, 58765, 327877, 1872490, 10890483, 64267612, 383773529, 2314271146, 14071475748, 86165249745, 530862665988, 3288219482754, 20464419717069, 127901478759153, 802421158028657 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..21.

FORMULA

G.f.: A(x) = C(x)*T(x) where C(x) = 1 + x*C(x)^2 is the g.f. of A000108 and T(x) = 1 + x*T(x)^3 is the g.f. of A001764.

PROG

(PARI) a(n)=sum(k=0, n, binomial(2*k, k)/(k+1)*binomial(3*(n-k), n-k)/(2*(n-k)+1))

CROSSREFS

Cf. A000108, A001764.

Sequence in context: A342293 A342291 A001181 * A279570 A338748 A107945

Adjacent sequences:  A130576 A130577 A130578 * A130580 A130581 A130582

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jun 07 2007

STATUS

approved

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Last modified April 19 02:19 EDT 2021. Contains 343105 sequences. (Running on oeis4.)