a(n) = 9*binomial(5*n+9, n)/(5*n+9).

Terms

a(0) =1a(1) =9a(2) =81a(3) =759a(4) =7371a(5) =73656a(6) =752913a(7) =7838298a(8) =82832706a(9) =886322710a(10) =9583986555a(11) =104568156819