a(n) = (3/2)^n * Sum_{k=0..n} (1/6)^k * (2*k)! * (n-k)! * binomial(n,k)^2.
A383280
a(n) = (3/2)^n * Sum_{k=0..n} (1/6)^k * (2*k)! * (n-k)! * binomial(n,k)^2.
Terms
- a(0) =1a(1) =2a(2) =9a(3) =72a(4) =954a(5) =19980a(6) =624510a(7) =27420120a(8) =1607036760a(9) =120942324720
External references
- oeis: A383280