a(n) = Sum_{k=0..floor(2*n/5)} binomial(3*k,2*n-5*k).

Terms

a(0) =1a(1) =0a(2) =0a(3) =3a(4) =1a(5) =1a(6) =15a(7) =15a(8) =10a(9) =84a(10) =127a(11) =102a(12) =496a(13) =939a(14) =950a(15) =3070a(16) =6589a(17) =8065a(18) =19950a(19) =45193a(20) =64109a(21) =135120a(22) =307616a(23) =487492a(24) =941887a(25) =2096251a(26) =3598606a(27) =6675696a(28) =14367175a(29) =26051277