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Search: id:A080925
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| 0, 1, 5, 13, 41, 121, 365, 1093, 3281, 9841, 29525, 88573, 265721, 797161, 2391485, 7174453, 21523361, 64570081, 193710245, 581130733, 1743392201, 5230176601, 15690529805, 47071589413, 141214768241, 423644304721, 1270932914165
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OFFSET
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0,3
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FORMULA
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a(n)=Sum{k=1..n, Binomial(n, 2k-2)2^(2k-2)}
a(n)=(3^n-2*0^n+(-1)^n)/2; G.f.: x(1+3x)/((1+x)(1-3x)); E.g.f.: (exp(3x)-2exp(0)+exp(-x))/2. - Paul Barry (pbarry(AT)wit.ie), May 19 2003
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CROSSREFS
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Cf. A046717, A080926.
Sequence in context: A080267 A034735 A046717 this_sequence A164907 A085601 A147718
Adjacent sequences: A080922 A080923 A080924 this_sequence A080926 A080927 A080928
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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), Feb 26 2003
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EXTENSIONS
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Removed duplicate of a formula - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 03 2009
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