Expansion (1-sqrt(1-4*x))/(2*(1-x^4-x)).

Terms

a(0) =1a(1) =2a(2) =4a(3) =9a(4) =24a(5) =68a(6) =204a(7) =642a(8) =2096a(9) =7026a(10) =24026a(11) =83454a(12) =293562a(13) =1043488a(14) =3741954a(15) =13520253a(16) =49171485a(17) =179859763a(18) =661240417a(19) =2442023860a(20) =9055315765a(21) =33701442548a(22) =125845246605a(23) =471346884115