G.f. satisfies A(x) = 1 / (1 - x^4*A(x)^4 * (1 + x)).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =1a(5) =1a(6) =0a(7) =0a(8) =5a(9) =10a(10) =5a(11) =0a(12) =35a(13) =105a(14) =105a(15) =35a(16) =285a(17) =1140a(18) =1710a(19) =1140a(20) =2815a(21) =12650a(22) =25300a(23) =25300a(24) =36401a(25) =145036a(26) =356265a(27) =475020a(28) =588145a(29) =1765666