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Search: id:A137941
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| A137941 |
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G.f.: exp(x) = Product_{n>=1} [1 + a(2n-1)*x^(2n-1)/(2n-1)! + a(2n)*x^(2n)/(2n)! ]. |
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+0
1
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| 1, 1, 1, -3, 6, 10, -195, 945, -3080, 17136, 37170, -796950, 3880800, 122007600, -2380685307, 18531377865, -136619683200, 942469528000, 723819456360, -118481659031736, 1884943573381440, -16067035945724400, -323306803861791750, 15940746503392961250
(list; graph; listen)
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OFFSET
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1,4
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COMMENT
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a(n) appears to be divisible by (n-1)(n-2)/2 for n>2.
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EXAMPLE
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exp(x) = (1 + 1*x + 1*x^2/2!) * (1 + 1*x^3/3! - 3*x^4/4!) * (1 + 6*x^5/5! + 10*x^6/6!) * (1 - 195*x^7/7! + 945*x^8/8!) *...
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PROGRAM
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(PARI) {a(n)=if(n<1, 0, n!*polcoeff(exp(x +x*O(x^n))/prod(k=1, (n-1)\2, 1+a(2*k-1)*x^(2*k-1)/(2*k-1)!+a(2*k)*x^(2*k)/(2*k)! +x*O(x^n)), n))}
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CROSSREFS
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Cf. A137852.
Sequence in context: A061380 A125567 A124266 this_sequence A077170 A079801 A083462
Adjacent sequences: A137938 A137939 A137940 this_sequence A137942 A137943 A137944
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KEYWORD
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sign
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Feb 23 2008
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