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A373906
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a(n) = Sum_{k=0..floor(n/4)} binomial(n+2*k,n-4*k).
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3
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1, 1, 1, 1, 2, 8, 29, 85, 212, 476, 1016, 2172, 4825, 11213, 26763, 64095, 151851, 354737, 820328, 1889968, 4361521, 10106859, 23509678, 54793282, 127709888, 297336790, 691382201, 1606284377, 3731020629, 8668253125, 20146856893, 46840732201, 108918637566, 253262275888
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OFFSET
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0,5
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LINKS
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FORMULA
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a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 14*a(n-4) + 6*a(n-5) - a(n-6).
G.f.: 1/(1 - x - x^4/(1 - x)^5).
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PROG
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(PARI) a(n) = sum(k=0, n\4, binomial(n+2*k, n-4*k));
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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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