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A371538
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G.f. A(x) satisfies A(x) = (1 + x*A(x)^2 / (1+x))^3.
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4
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1, 3, 18, 151, 1440, 14835, 160793, 1806849, 20859129, 245905348, 2947869600, 35825319390, 440372147956, 5465555197818, 68396554601013, 862066323857486, 10933638171672105, 139439595024315675, 1787056241039876890, 23003636498360053905, 297283046361025602900
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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) = 3 * Sum_{k=0..n} (-1)^(n-k) * binomial(n-1,n-k) * binomial(6*k+3,k)/(6*k+3).
G.f.: A(x) = B(x)^3 where B(x) is the g.f. of A349362.
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PROG
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(PARI) a(n) = 3*sum(k=0, n, (-1)^(n-k)*binomial(n-1, n-k)*binomial(6*k+3, k)/(6*k+3));
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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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