A206846 G.f.: exp( Sum_{n>=1} x^n/n * Sum_{k=0..n} binomial(n^2,k^2) * binomial(n^2,(n-k)^2) ).

1, 2, 11, 776, 921193, 10359730908, 1620677532919905, 1969126979596399128130, 32593711828578589304123599877, 3931730912701446701027876250509820962, 6413805618092047206104426809813307222469463650, 74040826359052943559114050244071546075856822107307951070

Offset

0,2

Comments

Logarithmic derivative yields A206847.

Links

Table of n, a(n) for n=0..11.

Example

G.f.: A(x) = 1 + 2*x + 11*x^2 + 776*x^3 + 921193*x^4 + 10359730908*x^5 +...
where the logarithm of the g.f. yields the l.g.f. of A206847:
log(A(x)) = 2*x + 18*x^2/2 + 2270*x^3/3 + 3678482*x^4/4 + 51789416252*x^5/5 +...

Prog

(PARI) {a(n)=polcoeff(exp(sum(m=1, n, sum(k=0, m, binomial(m^2, k^2)*binomial(m^2, (m-k)^2))*x^m/m)+x*O(x^n)), n)}
for(n=0, 25, print1(a(n), ", "))

Crossrefs

Cf. A206847 (log), A206848, A206850.

Sequence in context: A000886 A128855 A262547 * A092730 A157841 A293240

Adjacent sequences: A206843 A206844 A206845 * A206847 A206848 A206849

Keyword

nonn

Author

Paul D. Hanna, Feb 15 2012

Status

approved