a(0) = 1, a(1) = 2; for n>=2 a(n) is the number of degree-n reducible polynomials over GF(2).

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =13a(5) =26a(6) =55a(7) =110a(8) =226a(9) =456a(10) =925a(11) =1862a(12) =3761a(13) =7562a(14) =15223a(15) =30586a(16) =61456a(17) =123362a(18) =247612a(19) =496694a(20) =996199a(21) =1997294a(22) =4003747a(23) =8023886a(24) =16078346a(25) =32212256a(26) =64528069a(27) =129246720a(28) =258849061a(29) =518358122