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A364645
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G.f. satisfies A(x) = 1/(1 - 3*x) - x*A(x)^3.
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4
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1, 2, 3, 6, 19, 51, 114, 312, 981, 2616, 6564, 19647, 59922, 159056, 430302, 1329996, 3926217, 10498968, 30052851, 93244764, 267690168, 729649143, 2173840338, 6663260223, 18768583674, 52570016676, 160362713250, 481809941520, 1346473504182, 3886164785178
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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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a(n) = Sum_{k=0..n} (-1)^k * 3^(n-k) * binomial(n+k,2*k) * binomial(3*k,k) / (2*k+1).
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PROG
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(PARI) a(n) = sum(k=0, n, (-1)^k*3^(n-k)*binomial(n+k, 2*k)*binomial(3*k, k)/(2*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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