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A365733
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G.f. satisfies A(x) = 1 + x*A(x)*(1 + x^5*A(x)^3).
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3
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1, 1, 1, 1, 1, 1, 2, 6, 16, 36, 71, 127, 215, 367, 676, 1376, 2982, 6514, 13855, 28407, 56543, 111127, 219918, 444450, 919744, 1933732, 4082467, 8576027, 17861347, 36938427, 76207797, 157652981, 328119005, 687377565, 1446665765, 3050094661, 6427116181
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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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a(n) = Sum_{k=0..floor(n/6)} binomial(n-5*k,k) * binomial(n-2*k+1,n-5*k) / (n-2*k+1) = Sum_{k=0..floor(n/6)} binomial(n-2*k,4*k) * binomial(4*k,k) / (3*k+1).
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PROG
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(PARI) a(n) = sum(k=0, n\6, binomial(n-5*k, k)*binomial(n-2*k+1, n-5*k)/(n-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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