login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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 (list; graph; refs; listen; history; text; internal format)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 3 22:32 EST 2021. Contains 349468 sequences. (Running on oeis4.)