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Search: id:A107232
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| A107232 |
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Expansion of (1+xc(x^2))^3/sqrt(1-4x^2), c(x) the g.f. of A000108. |
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+0
1
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| 1, 3, 5, 10, 18, 35, 65, 126, 238, 462, 882, 1716, 3300, 6435, 12441, 24310, 47190, 92378, 179894, 352716, 688636, 1352078, 2645370, 5200300, 10192588, 20058300, 39373700, 77558760, 152443080, 300540195, 591385545, 1166803110, 2298248550
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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An inverse Chebyshev transform of C(3,n)=(1,3,3,1,0,0,0,...), where g(x)->(1/sqrt(1-4x^2))g(xc(x^2)). In general, (1+xc(x^2))^r/sqrt(1-4x^2) has general term a(n)=sum{k=0..floor(n/2), binomial(n,k)*binomial(r,n-2k)}, r>0.
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FORMULA
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a(n)=sum{k=0..floor(n/2), binomial(n, k)*binomial(3, n-2k)}
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CROSSREFS
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Adjacent sequences: A107229 A107230 A107231 this_sequence A107233 A107234 A107235
Sequence in context: A054179 A010049 A094986 this_sequence A134522 A001445 A125750
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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), May 13 2005
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