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 A191423 E.g.f. (1+x+x^2+x^3)^x 0
 1, 0, 2, 3, 20, -30, 594, -840, 14384, -167832, 2300040, -17190360, 153272712, -2775904560, 51294972624, -651268374120, 7597950113280, -151775259773760, 3587640413505984, -63586583168595840, 972086975299451520 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS FORMULA a(n)=(sum(m=1..n, sum(k=0..n-2*m, (stirling1(m+k,m)*sum(j=0..m+k, binomial(j,n-3*(m+k)-m+2*j)*binomial(m+k,j)))/(m+k)!)))*n!, n>0, a(0)=1. PROG (Maxima) a(n):=(sum(sum((stirling1(m+k, m)*sum(binomial(j, n-3*(m+k)-m+2*j)*binomial(m+k, j), j, 0, m+k))/(m+k)!, k, 0, n-2*m), m, 1, n))*n!; CROSSREFS Sequence in context: A154746 A042781 A136886 * A195686 A072472 A233410 Adjacent sequences:  A191420 A191421 A191422 * A191424 A191425 A191426 KEYWORD sign AUTHOR Vladimir Kruchinin, Jun 02 2011 STATUS approved

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