a(n) = Sum_{k=0..floor(3*n/8)} binomial(k+2,2) * binomial(k,3*n-8*k).

Terms

a(0) =1a(1) =0a(2) =0a(3) =3a(4) =0a(5) =0a(6) =6a(7) =0a(8) =10a(9) =10a(10) =0a(11) =60a(12) =15a(13) =0a(14) =210a(15) =21a(16) =28a(17) =560a(18) =28a(19) =252a(20) =1260a(21) =36a(22) =1260a(23) =2520a(24) =100a(25) =4620a(26) =4620a(27) =715a(28) =13860a(29) =7920