A187116 A diagonal of triangle A187115.

1, 4, 20, 138, 1258, 14476, 202655, 3354848, 64246776, 1398909332, 34157026526, 924757926320, 27503093599024, 891534666547216, 31289986924954924, 1182213869836721036, 47846600590876178320, 2065282617724684345208

Offset: 2

Author

Paul D. Hanna, Mar 08 2011

Keywords

• nonn

Comments

Definition of triangle: A187115(n,k) = [y^k] R_{n-1}(y+y^2) for k=2..n, n>2, where R_n(y) is the n-th row polynomial with R_2(y)=y^2.

Crossrefs

Cf. A187115, A135082, A187117, A187118, A187119.

Programs

PARI

{a(n)=local(Rn=y^2);for(m=2,n+1,Rn=subst(truncate(Rn),y,y+y^2+O(y^m)));polcoeff(Rn,n,y)}

Formula

Equals column 1 in the matrix square of triangle A135080.