a(n) = (n!)^2 * Sum_{k=0..n} (k+1) / ((n-k)!)^2.
A336809
a(n) = (n!)^2 * Sum_{k=0..n} (k+1) / ((n-k)!)^2.
Terms
- a(0) =1a(1) =3a(2) =21a(3) =271a(4) =5649a(5) =174051a(6) =7447573a(7) =422836191a(8) =30767443521
External references
- oeis: A336809
A336809
a(n) = (n!)^2 * Sum_{k=0..n} (k+1) / ((n-k)!)^2.