a(n) = 2*binomial(9*n+2,n)/(9*n+2).

A234505

a(n) = 2*binomial(9*n+2,n)/(9*n+2).

Terms

    a(0) =1a(1) =2a(2) =19a(3) =252a(4) =3885a(5) =65274a(6) =1159587a(7) =21421248a(8) =407337153a(9) =7920326700a(10) =156753610013

External references