a(n) = (1/2) * Sum_{k=1..n} (n+k)!/(k!)^2.
A073013
a(n) = (1/2) * Sum_{k=1..n} (n+k)!/(k!)^2.
Terms
- a(0) =1a(1) =6a(2) =37a(3) =255a(4) =1991a(5) =17598a(6) =174924a(7) =1937715a(8) =23696029a(9) =317105778a(10) =4608337064a(11) =72249308222
External references
- oeis: A073013