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 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: A362274 A328978 A185655 * A303559 A161120 A183430 Adjacent sequences: A181143 A181144 A181145 * A181147 A181148 A181149 KEYWORD nonn AUTHOR Paul D. Hanna, Oct 16 2010 STATUS approved

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Last modified May 20 10:51 EDT 2024. Contains 372712 sequences. (Running on oeis4.)