a(n) = 3*binomial(4*n+8, n)/(n+3).

Terms

a(0) =1a(1) =9a(2) =72a(3) =570a(4) =4554a(5) =36855a(6) =302064a(7) =2504304a(8) =20974005a(9) =177232627a(10) =1509395976a(11) =12943656180a(12) =111676661460a(13) =968786892675