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A366588
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G.f. A(x) satisfies A(x) = 1 + x^3*(1+x)*A(x)^2.
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2
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1, 0, 0, 1, 1, 0, 2, 4, 2, 5, 15, 15, 19, 56, 84, 98, 224, 420, 552, 1002, 2022, 3069, 4983, 9801, 16577, 26455, 49049, 87945, 144287, 255112, 465244, 792012, 1369862, 2482714, 4348838, 7509580, 13439724, 23911044, 41643744, 73832632, 132039816, 232391394
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OFFSET
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0,7
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LINKS
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FORMULA
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G.f.: A(x) = 2 / (1+sqrt(1-4*x^3*(1+x))).
a(n) = Sum_{k=0..floor(n/3)} binomial(k,n-3*k) * binomial(2*k,k)/(k+1).
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PROG
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(PARI) a(n) = sum(k=0, n\3, binomial(k, n-3*k)*binomial(2*k, k)/(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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