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Search: id:A112240
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| A112240 |
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Expansion of exp(x/(1-x-2x^2)). |
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+0
1
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| 1, 1, 3, 25, 217, 2541, 34531, 550453, 9957585, 202137337, 4543312771, 112004037201, 3003936136873, 87057179039845, 2710682505789987, 90230919126896941, 3197152300287286561, 120131212083966304113
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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In general, e.g.f. exp(x/(1-ax-bx^2)) has general term n!*sum{i=0..n, sum{j=0..n, a^j*(b/a)^(n-i-j)*C(i+j-1,j)C(j,n-i-j)/i!}}.
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FORMULA
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E.g.f. exp(x/(1-x-x^2)); a(n)=n!*sum{i=0..n, sum{j=0..n, 2^(n-i-j)*C(i+j-1, j)C(j, n-i-j)/i!}};
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CROSSREFS
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Sequence in context: A037664 A037783 A037587 this_sequence A155640 A024217 A118726
Adjacent sequences: A112237 A112238 A112239 this_sequence A112241 A112242 A112243
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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), Aug 29 2005
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