G.f.: Sum_{n>=0} n!^2 * x^n / Product_{k=1..n} (1 + k*x)^2.
A216860
G.f.: Sum_{n>=0} n!^2 * x^n / Product_{k=1..n} (1 + k*x)^2.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =15a(4) =232a(5) =5693a(6) =202398a(7) =9829771a(8) =624964724a(9) =50365047225
External references
- oeis: A216860