a(n) = (1/(2n+1))*Multinomial(3n; n,n,n).
A024486
a(n) = (1/(2n+1))*Multinomial(3n; n,n,n).
Terms
- a(0) =1a(1) =2a(2) =18a(3) =240a(4) =3850a(5) =68796a(6) =1319472a(7) =26604864a(8) =556794810a(9) =11993338500a(10) =264333180540
External references
- oeis: A024486