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A367111
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G.f. satisfies A(x) = 1 + x*A(x) + 2*x^3*A(x)^3.
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3
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1, 1, 1, 3, 9, 21, 53, 155, 449, 1273, 3721, 11155, 33529, 101245, 309037, 950587, 2936833, 9117169, 28448209, 89134435, 280252585, 884123429, 2797933733, 8879167067, 28249550913, 90091462761, 287946752601, 922194331891, 2959055180953, 9511538457229
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OFFSET
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0,4
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LINKS
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FORMULA
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a(n) = Sum_{k=0..floor(n/3)} 2^k * binomial(n,3*k) * A001764(k).
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PROG
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(PARI) a(n) = sum(k=0, n\3, 2^k*binomial(n, 3*k)*binomial(3*k, k)/(2*k+1));
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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