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A375362
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Expansion of 1/( (1 + x) * (1 - x*(1 + x)^3) ).
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1
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1, 0, 4, 6, 20, 49, 132, 344, 908, 2384, 6273, 16492, 43372, 114050, 299916, 788673, 2073944, 5453760, 14341528, 37713312, 99173121, 260791400, 685792228, 1803399102, 4742323108, 12470688497, 32793647356, 86236081272, 226771411940, 596331286320
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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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a(n) = 4*a(n-2) + 6*a(n-3) + 4*a(n-4) + a(n-5).
a(n) = Sum_{k=0..n} binomial(3*k-1,n-k).
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PROG
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(PARI) my(N=30, x='x+O('x^N)); Vec(1/((1+x)*(1-x*(1+x)^3)))
(PARI) a(n) = sum(k=0, n, binomial(3*k-1, n-k));
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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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