a(n) = Sum_{k=0..floor(n/4)} binomial(n-1-3*k,n-4*k) * binomial(2*k,k).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =2a(5) =2a(6) =2a(7) =2a(8) =8a(9) =14a(10) =20a(11) =26a(12) =52a(13) =98a(14) =164a(15) =250a(16) =426a(17) =762a(18) =1328a(19) =2194a(20) =3682a(21) =6366a(22) =11072a(23) =18878a(24) =32038a(25) =54906a(26) =94860a(27) =163226a(28) =279634a(29) =479806