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A130579
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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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0
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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
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OFFSET
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0,2
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LINKS
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FORMULA
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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.
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PROG
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(PARI) a(n)=sum(k=0, n, binomial(2*k, k)/(k+1)*binomial(3*(n-k), n-k)/(2*(n-k)+1))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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