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A371661
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G.f. satisfies A(x) = 1 + x * A(x)^3 * (1 + A(x))^2.
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5
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1, 4, 64, 1424, 36800, 1036160, 30843648, 954671360, 30415326208, 990831196160, 32853724512256, 1105132250898432, 37620337933582336, 1293586791397064704, 44863864476704768000, 1567543145774827241472, 55125711913212153954304
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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) = (1/n) * Sum_{k=0..floor(n-1)/2} 4^(n-k) * binomial(n,k) * binomial(4*n-k,n-1-2*k) for n > 0.
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PROG
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(PARI) a(n) = if(n==0, 1, sum(k=0, (n-1)\2, 4^(n-k)*binomial(n, k)*binomial(4*n-k, n-1-2*k))/n);
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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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