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Search: id:A008464
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| 1, 5, 24, 108, 464, 1936, 7936, 32192, 129792, 521472, 2091008, 8375296, 33525760, 134156288, 536739840, 2147205120, 8589344768, 34358493184, 137436332032, 549750308864, 2199011721216, 8796068904960
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OFFSET
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-1,2
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COMMENT
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a(n-2)=2^(2n-1) - (n+1)*2^(n-2) is number of compositions of 2n where each part is less than or equal to n: e.g. for n=2, 4 can be written 5 ways with no part greater than 2 as 1+1+1+1=1+1+2=1+2+1=2+1+1=2+2. - Henry Bottomley (se16(AT)btinternet.com), Feb 03 2003
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FORMULA
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G.f.: 8/(1-4x)-3/(1-2x)-2x/(1-2x)^2+1/x. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Nov 21 2007
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MAPLE
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f := n->2^(2*n+3)-2^n*(n+3);
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CROSSREFS
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Sequence in context: A099653 A078820 A046724 this_sequence A063001 A000953 A081104
Adjacent sequences: A008461 A008462 A008463 this_sequence A008465 A008466 A008467
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KEYWORD
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nonn,easy
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AUTHOR
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njas
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