Number of "semiperiodic" binary words of length n.

Terms

a(0) =2a(1) =2a(2) =4a(3) =4a(4) =10a(5) =14a(6) =22a(7) =32a(8) =70a(9) =122a(10) =178a(11) =286a(12) =518a(13) =898a(14) =1610a(15) =2666a(16) =4702a(17) =8506a(18) =14982a(19) =26668a(20) =48022a(21) =85904a(22) =155102a(23) =282096a(24) =514510a(25) =944036a(26) =1734736a(27) =3194838a(28) =5898576a(29) =10945970