OFFSET
0,2
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 ).
EXAMPLE
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.
PROG
(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)}
CROSSREFS
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Oct 16 2010
STATUS
approved