

A185757


Column 2 of triangle A185755.


4



6, 120, 2340, 49315, 1142932, 29141994, 814059798, 24779916843, 817506518829, 29081010732059, 1110248649302494, 45298134089851175, 1967550159430960784, 90668183653348456484, 4418855084158930131012, 227122154996245283660487
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OFFSET

1,1


COMMENTS

A185755(n,k) equals the coefficient of x^n*y^k in the nth iteration of x*(1+xy)/(1x).


LINKS

Table of n, a(n) for n=1..16.


PROG

(PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1x)); for(i=1, n+2, A=subst(G, x, A+O(x^(n+3)))); polcoeff(polcoeff(A, n+2, x), 2, y)}


CROSSREFS

Cf. A185755, A185756, A185758, A185759.
Sequence in context: A065888 A246191 A246611 * A075844 A029697 A248045
Adjacent sequences: A185754 A185755 A185756 * A185758 A185759 A185760


KEYWORD

nonn


AUTHOR

Paul D. Hanna, Feb 03 2011


STATUS

approved



