a(n) is number of cycles in Moebius ladder M_n.

Terms

a(0) =2a(1) =3a(2) =7a(3) =15a(4) =29a(5) =53a(6) =95a(7) =171a(8) =313a(9) =585a(10) =1115a(11) =2159a(12) =4229a(13) =8349a(14) =16567a(15) =32979a(16) =65777a(17) =131345a(18) =262451a(19) =524631a(20) =1048957a(21) =2097573a(22) =4194767a(23) =8389115a(24) =16777769a(25) =33555033a(26) =67109515a(27) =134218431a(28) =268436213a(29) =536871725