a(n) = Sum_{k=0..n} binomial(3*k,k)*binomial(3*n-3*k,n-k).
A006256
a(n) = Sum_{k=0..n} binomial(3*k,k)*binomial(3*n-3*k,n-k).
Terms
- a(0) =1a(1) =6a(2) =39a(3) =258a(4) =1719a(5) =11496a(6) =77052a(7) =517194a(8) =3475071a(9) =23366598a(10) =157206519a(11) =1058119992a(12) =7124428836a(13) =47983020624a(14) =323240752272
External references
- oeis: A006256