a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n,k) * binomial(3*n,k).
A387931
a(n) = Sum_{k=0..n} 3^(n-k) * binomial(n,k) * binomial(3*n,k).
Terms
- a(0) =1a(1) =6a(2) =60a(3) =678a(4) =8076a(5) =99096a(6) =1239396a(7) =15709140a(8) =201078396a(9) =2593341768a(10) =33647629680a(11) =438693096870
External references
- oeis: A387931