a(n) = Sum_{k=0..n} (-1)^k * binomial(2*n+k-1,k) * binomial(6*n-k-1,n-k).

A370104

a(n) = Sum_{k=0..n} (-1)^k * binomial(2*n+k-1,k) * binomial(6*n-k-1,n-k).

Terms

    a(0) =1a(1) =3a(2) =25a(3) =219a(4) =2025a(5) =19253a(6) =186469a(7) =1829565a(8) =18124521a(9) =180886260a(10) =1815946275a(11) =18318160358a(12) =185518492965

External references