A181146 Main diagonal of triangle A181145.

1, 4, 27, 236, 2380, 26216, 306495, 3740572, 47159772, 609924536, 8051939324, 108110654120, 1472276038688, 20292738170064, 282614171731527, 3971576995998588, 56256063139701916, 802448704561822616

Offset: 0

Author

Paul D. Hanna, Oct 16 2010

Keywords

• nonn

Comments

Triangle A181145 is formed from the coefficients of the g.f.:

* exp( Sum_{n>=1} [Sum_{k=0..2n} C(2n,k)^2*y^k]*x^n/n ).

Examples

			Triangle A181145 begins:
(1);
1,(4), 1;
1, 12,(27), 12, 1;
1, 24, 134,(236), 134, 24, 1;
1, 40, 410, 1540,(2380), 1540, 410, 40, 1;
1, 60, 975, 6260, 18386,(26216), 18386, 6260, 975, 60, 1; ...
in which this sequence equals the central terms of the rows.
		

Crossrefs

Cf. A181146.

Programs

PARI

{a(n)=polcoeff(polcoeff(exp(sum(m=1,n,sum(j=0,2*m,binomial(2*m,j)^2*y^j)*x^m/m)+O(x^(n+1))),n,x),n,y)}