id:A130579 - OEIS Search Results

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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)].

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1, 2, 6, 22, 92, 423, 2087, 10856, 58765, 327877, 1872490, 10890483, 64267612, 383773529, 2314271146, 14071475748, 86165249745, 530862665988, 3288219482754, 20464419717069, 127901478759153, 802421158028657 (list; graph; listen)

	OFFSET	`0,2`
	FORMULA	`G.f.: A(x) = C(x)T(x) where C(x) = 1 + xC(x)^2 is the g.f. of A000108 and T(x) = 1 + x*T(x)^3 is the g.f. of A001764.`
	PROGRAM	`(PARI) a(n)=sum(k=0, n, binomial(2k, k)/(k+1)binomial(3(n-k), n-k)/(2(n-k)+1))`
	CROSSREFS	`Cf. A000108, A001764.` `Sequence in context: A124293 A107591 A001181 this_sequence A107945 A014330 A124294` `Adjacent sequences: A130576 A130577 A130578 this_sequence A130580 A130581 A130582`
	KEYWORD	`nonn`
	AUTHOR	`Paul D. Hanna (pauldhanna(AT)juno.com), Jun 07 2007`

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Last modified July 26 13:41 EDT 2008. Contains 142293 sequences.

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