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) =1a(7) =1a(8) =6a(9) =11a(10) =16a(11) =21a(12) =61a(13) =136a(14) =246a(15) =391a(16) =856a(17) =1926a(18) =3886a(19) =7021a(20) =14146a(21) =30606a(22) =64276a(23) =125561a(24) =251147a(25) =527752a(26) =1115877a(27) =2273557a(28) =4611992a(29) =9583058