a(n) = 2/n^2*( sum_{k=0..n-1} (2*k+1)*C(n-1,k)^2*C(n+k,k) ), where C(m,k) denotes the binomial coefficient m!/(k!*(m-k)!).
A246542
a(n) = 2/n^2*( sum_{k=0..n-1} (2*k+1)*C(n-1,k)^2*C(n+k,k) ), where C(m,k) denotes the binomial coefficient m!/(k!*(m-k)!).
Terms
- a(0) =2a(1) =5a(2) =22a(3) =132a(4) =918a(5) =6981a(6) =56390a(7) =475796a(8) =4149286a(9) =37133043a(10) =339307098a(11) =3154030050a(12) =29741815998a(13) =283896719073
External references
- oeis: A246542