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A185756
Column 1 of triangle A185755.
4
2, 15, 154, 1995, 31191, 571221, 11992688, 283976517, 7487521975, 217567092743, 6907888374828, 237951469523807, 8838510559556783, 352160268261051113, 14982705940607112640, 677935029521206050505, 32508195354031791206799
OFFSET
1,1
COMMENTS
Column 0 of triangle A185755 equals n^(n-1).
A185755(n,k) equals the coefficient of x^n*y^k in the n-th iteration of x*(1+xy)/(1-x).
PROG
(PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1-x)); for(i=1, n+1, A=subst(G, x, A+O(x^(n+2)))); polcoeff(polcoeff(A, n+1, x), 1, y)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 03 2011
STATUS
approved