G.f. A(x) satisfies A(x)^2 = A(x^2) / (1 - 2*x)^2 with A(0)=1.

Terms

a(0) =1a(1) =2a(2) =5a(3) =10a(4) =22a(5) =44a(6) =91a(7) =182a(8) =370a(9) =740a(10) =1490a(11) =2980a(12) =5979a(13) =11958a(14) =23950a(15) =47900a(16) =95865a(17) =191730a(18) =383580a(19) =767160a(20) =1534549a(21) =3069098a(22) =6138628a(23) =12277256a(24) =24555341a(25) =49110682a(26) =98222947a(27) =196445894a(28) =392894839a(29) =785789678