G.f.: (x-1)/(-2*x^2 + 3*x^3 + 2*x - 1).

Terms

a(0) =1a(1) =1a(2) =0a(3) =1a(4) =5a(5) =8a(6) =9a(7) =17a(8) =40a(9) =73a(10) =117a(11) =208a(12) =401a(13) =737a(14) =1296a(15) =2321a(16) =4261a(17) =7768a(18) =13977a(19) =25201a(20) =45752a(21) =83033a(22) =150165a(23) =271520a(24) =491809a(25) =891073a(26) =1613088a(27) =2919457a(28) =5285957a(29) =9572264