a(n) = n! * Sum_{k=1..n} binomial(2n+1,k)/k.
A129840
a(n) = n! * Sum_{k=1..n} binomial(2n+1,k)/k.
Terms
- a(0) =3a(1) =20a(2) =175a(3) =2076a(4) =32208a(5) =626028a(6) =14688924a(7) =404166432a(8) =12756813408a(9) =454171720320
External references
- oeis: A129840