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A099559
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a(n) = Sum_{k=0..floor(n/5)} C(n-4k,k+1).
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2
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0, 1, 2, 3, 4, 5, 7, 10, 14, 19, 25, 33, 44, 59, 79, 105, 139, 184, 244, 324, 430, 570, 755, 1000, 1325, 1756, 2327, 3083, 4084, 5410, 7167, 9495, 12579, 16664, 22075, 29243, 38739, 51319, 67984, 90060, 119304, 158044, 209364, 277349, 367410, 486715
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OFFSET
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0,3
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LINKS
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FORMULA
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Partial sums of A003520 (with leading zero).
G.f.: x / ( (x-1)*(x^2-x+1)*(x^3+x^2-1) ).
a(n) = 2a(n-1)-a(n-2)+a(n-5)-a(n-6).
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MATHEMATICA
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LinearRecurrence[{2, -1, 0, 0, 1, -1}, {0, 1, 2, 3, 4, 5}, 50] (* Harvey P. Dale, Feb 20 2017 *)
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PROG
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(PARI) a(n) = sum(k=0, n\5, binomial(n-4*k, k+1)); \\ Michel Marcus, Jul 11 2018
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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