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A092429
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a(n)=n!*sum(i+j+k+l=n,1/(i!*j!*k!*l!)) (i,j,k,l>=0).
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0
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1, 1, 3, 10, 47, 126, 522, 1821, 8143, 26326, 109958, 396111, 1737122, 5998955, 24949277, 91979985, 397402223, 1418993350, 5881338702, 22010456331, 94022106862, 342803313261, 1416758002487, 5356198979731, 22685035586290
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,3
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COMMENTS
| a(n) is even iff n is a sum of 2 distinct powers of 2
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FORMULA
| E.g.f.: (t(1)^4+6*t(1)^2*t(2)+8*t(1)*t(3)+3*t(2)^2+6*t(4))/24 where t(1)=hypergeom([],[],x), t(2)=hypergeom([],[1],x^2), t(3)=hypergeom([],[1,1],x^3) and t(3)=hypergeom([],[1,1,1],x^4). - Vladeta Jovovic (vladeta(AT)eunet.rs), Sep 22 2007
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PROG
| (PARI) a(n)=sum(i=0, n, sum(j=0, i, sum(k=0, j, sum(l=0, k, if(i+j+k+l-n, 0, n!/i!/j!/k!/l!)))))
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CROSSREFS
| Cf. A018900, A092255.
Sequence in context: A020008 A167999 A000849 * A005651 A105748 A140964
Adjacent sequences: A092426 A092427 A092428 * A092430 A092431 A092432
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KEYWORD
| nonn
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AUTHOR
| Benoit Cloitre (benoit7848c(AT)orange.fr), Mar 22 2004
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