a(n) = 3*binomial(10*n+3,n)/(10*n+3).

A234526

a(n) = 3*binomial(10*n+3,n)/(10*n+3).

Terms

    a(0) =1a(1) =3a(2) =33a(3) =496a(4) =8610a(5) =162435a(6) =3235501a(7) =66959532a(8) =1425658806a(9) =31026962395a(10) =687124547340

External references