a(n) = (2/((n+1)*(n+2)))*multinomial(3*n;n,n,n).
A324151
a(n) = (2/((n+1)*(n+2)))*multinomial(3*n;n,n,n).
Terms
- a(0) =1a(1) =2a(2) =15a(3) =168a(4) =2310a(5) =36036a(6) =612612a(7) =11085360a(8) =210344706a(9) =4143153300a(10) =84106011990
External references
- oeis: A324151