A120917 - OEIS

A120917

Central terms of triangle A120914 (cascadence of (1+2x)^2).

1, 4, 32, 212, 1504, 10848, 79696, 596160, 4520000, 34673940, 268538048, 2096374656, 16475970896, 130234435648, 1034568731408, 8254368150320, 66112337392256, 531345216883584, 4283682906179728, 34632004320564416

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OFFSET

0,2

LINKS

Table of n, a(n) for n=0..19.

PROG

(PARI) {a(n)=local(A, F=1+4*x+4*x^2, d=2, G=x, H=1+x, S=ceil(log(n+1)/log(d+1))); for(i=0, n, G=x*subst(F, x, G+x*O(x^n))); for(i=0, S, H=subst(H, x, x*G^d+x*O(x^n))*G/x); A=(x*H-y*subst(H, x, x*y^d +x*O(x^n)))/(x*subst(F, x, y)-y); polcoeff(polcoeff(A, n, x), n, y)}

CROSSREFS

Cf. A120914, A120915, A120916, A120918.

Sequence in context: A248216 A133642 A098981 * A305518 A298965 A316955

Adjacent sequences: A120914 A120915 A120916 * A120918 A120919 A120920

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Jul 17 2006

STATUS

approved