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A124381
O.g.f.: A(x) = Sum_{n>=0} x^n*Product_{k=0..n} (1 + k*(k+1)/2*x).
0
1, 1, 2, 5, 14, 48, 181, 772, 3620, 18511, 102869, 613584, 3926895, 26734671, 193310243, 1477081245, 11896869336, 100700815331, 893438783126, 8291513009130, 80302486087937, 810290260679230, 8502192961792190
OFFSET
0,3
EXAMPLE
A(x) = 1 + x*(1+x) + x^2*(1+x)*(1+3x) + x^3*(1+x)*(1+3x)*(1+6x) +...
PROG
(PARI) a(n)=polcoeff(sum(k=0, n, x^k*prod(j=0, k, 1+j*(j+1)/2*x+x*O(x^n))), n)
CROSSREFS
Sequence in context: A149906 A129778 A060797 * A131236 A119499 A079452
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 28 2006
STATUS
approved