

A181146


Main diagonal of triangle A181145.


2



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


LINKS

Table of n, a(n) for n=0..17.


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

Cf. A181146.
Sequence in context: A160883 A328978 A185655 * A303559 A161120 A183430
Adjacent sequences: A181143 A181144 A181145 * A181147 A181148 A181149


KEYWORD

nonn


AUTHOR

Paul D. Hanna, Oct 16 2010


STATUS

approved



