a(n) = Sum_{k=0..floor(3*n/5)} (k+1) * binomial(k,3*n-5*k).

Terms

a(0) =1a(1) =0a(2) =2a(3) =0a(4) =3a(5) =4a(6) =4a(7) =20a(8) =5a(9) =60a(10) =13a(11) =140a(12) =63a(13) =280a(14) =260a(15) =514a(16) =849a(17) =950a(18) =2320a(19) =1980a(20) =5568a(21) =4840a(22) =12206a(23) =12870a(24) =25402a(25) =34050a(26) =52339a(27) =85812a(28) =111035a(29) =204208