a(n) = Sum_{k=0..n} (2*n-k)!*2^(k-n)/k!.
A202950
a(n) = Sum_{k=0..n} (2*n-k)!*2^(k-n)/k!.
Terms
- a(0) =1a(1) =2a(2) =10a(3) =127a(4) =3251a(5) =138826a(6) =8853202a(7) =786297485a(8) =92660657077
External references
- oeis: A202950
A202950
a(n) = Sum_{k=0..n} (2*n-k)!*2^(k-n)/k!.