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Search: id:A137220
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| 1, 4, 75, 2712, 116681, 5366384, 256461703, 12582521536, 629390010177, 31955248465164, 1641724961412515, 85159811886281576, 4452782349821587705, 234393562420377364008, 12409423916987553634575, 660253088667255226947072
(list; graph; listen)
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OFFSET
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0,2
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FORMULA
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a(n) = -Sum(binomial(-binomial(m,n),3)/2^(m+1),m=0..infinity).
a(n)=A137219(n)+A001850(n). - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 01 2008
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MAPLE
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A126086 := proc(n) local x, y, z ; coeftayl(coeftayl(coeftayl(1/(1-x-y-z-x*y-x*z-y*z-x*y*z), z=0, n), y=0, n), x=0, n) ; end: A001850 := proc(n) local k ; add(binomial(n, k)*binomial(n+k, k), k=0..n) ; end: A137220 := proc(n) (A126086(n)+3*A001850(n)+2)/6 ; end: seq(A137220(n), n=0..30) ; - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 01 2008
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CROSSREFS
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Cf. A047665, A137219.
Adjacent sequences: A137217 A137218 A137219 this_sequence A137221 A137222 A137223
Sequence in context: A046057 A072373 A006412 this_sequence A006236 A120248 A100323
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KEYWORD
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easy,nonn
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AUTHOR
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Vladeta Jovovic (vladeta(AT)Eunet.yu), Mar 06 2008, Mar 16 2008
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EXTENSIONS
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More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Apr 01 2008
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