a(n) = 2^(n-1) * Sum_{k=0..n} (n+k)! / k!^2.
A072343
a(n) = 2^(n-1) * Sum_{k=0..n} (n+k)! / k!^2.
Terms
- a(0) =3a(1) =28a(2) =320a(3) =4272a(4) =65632a(5) =1149312a(6) =22712832a(7) =501216000a(8) =12225264128a(9) =326574262272
External references
- oeis: A072343