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Search: id:A126042
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| A126042 |
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Expansion of f(x^3)/(1-x*f(x^3)), f(x) the g.f. of A001764, C(3n,n)/(2n+1). |
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+0
2
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| 1, 1, 1, 2, 3, 4, 8, 13, 19, 38, 64, 98, 196, 337, 531, 1062, 1851, 2974, 5948, 10468, 17060, 34120, 60488, 99658, 199316, 355369, 590563, 1181126, 2115577, 3540464, 7080928, 12731141, 21430267, 42860534, 77306428, 130771376
(list; graph; listen)
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OFFSET
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0,4
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COMMENT
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Row sums of number triangle A111373. Interleaves T(3n,2n),T(3n+1,2n+1) and T(3n+2,2n+2) for T(n,k)=A047089(n,k).
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FORMULA
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a(n)=sum{k=0..n,C(3*floor((n+2k)/3)-2k,floor((n+2k)/3)-k)*(k+1)/(2*floor((n+2k)/3)-k+ 1)(2*cos(2*pi*(n-k)/3)+1)/3};
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CROSSREFS
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Sequence in context: A095705 A034776 A068791 this_sequence A076227 A092075 A091415
Adjacent sequences: A126039 A126040 A126041 this_sequence A126043 A126044 A126045
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KEYWORD
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easy,nonn
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AUTHOR
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Paul Barry (pbarry(AT)wit.ie), Dec 16 2006
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