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A181146
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Main diagonal of triangle A181145.
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2
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1, 4, 27, 236, 2380, 26216, 306495, 3740572, 47159772, 609924536, 8051939324, 108110654120, 1472276038688, 20292738170064, 282614171731527, 3971576995998588, 56256063139701916, 802448704561822616
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OFFSET
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0,2
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COMMENTS
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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 ).
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LINKS
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EXAMPLE
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(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.
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PROG
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(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)}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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