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A118805
G.f.: 1 = Sum_{n>=0} a(n)*x^n*Product_{k=1..n} (1-k*x)^2.
3
1, 2, 11, 106, 1506, 28736, 694719, 20452602, 712529978, 28746803264, 1320665162746, 68164569542628, 3909330000805268, 246855506805662816, 17030177827550184395, 1275139722566251183642, 103032621304705343054010
OFFSET
0,2
LINKS
EXAMPLE
1 = 1*(1-x)^2 + 2*x*((1-x)(1-2x))^2 + 11*x^2*((1-x)(1-2x)(1-3x))^2 + ... + a(n)*x^n*((1-x)(1-2x)(1-3x)...(1-n*x))^2 + ...
PROG
(PARI) {a(n)=if(n==0, 1, polcoeff(1-sum(k=0, n-1, a(k)*x^k*prod(j=1, k+1, 1-j*x+x*O(x^n))^2), n))}
CROSSREFS
Cf. A118804 (variant).
Sequence in context: A278070 A292428 A088690 * A198001 A207155 A292566
KEYWORD
nonn
AUTHOR
Paul D. Hanna, May 02 2006
STATUS
approved