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A185757 Column 2 of triangle A185755. 4
6, 120, 2340, 49315, 1142932, 29141994, 814059798, 24779916843, 817506518829, 29081010732059, 1110248649302494, 45298134089851175, 1967550159430960784, 90668183653348456484, 4418855084158930131012, 227122154996245283660487 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

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

LINKS

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

PROG

(PARI) {a(n)=local(A=x, G=x*(1+x*y)/(1-x)); 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

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Last modified December 14 15:08 EST 2019. Contains 329979 sequences. (Running on oeis4.)