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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
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).
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
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Feb 03 2011
STATUS
approved