Expansion of g.f.: (1-2*x) / ((x-1)*(4*x^2+2*x-1)).

Terms

a(0) =1a(1) =1a(2) =5a(3) =13a(4) =45a(5) =141a(6) =461a(7) =1485a(8) =4813a(9) =15565a(10) =50381a(11) =163021a(12) =527565a(13) =1707213a(14) =5524685a(15) =17878221a(16) =57855181a(17) =187223245a(18) =605867213a(19) =1960627405a(20) =6344723661a(21) =20531956941a(22) =66442808525a(23) =215013444813a(24) =695798123725