a(n) = (n!)^2 * Sum_{k=1..n} binomial(n,k) / k^2.

A294117

a(n) = (n!)^2 * Sum_{k=1..n} binomial(n,k) / k^2.

Terms

    a(0) =1a(1) =9a(2) =139a(3) =3460a(4) =129076a(5) =6831216a(6) =492314544a(7) =46810296576

External references