Number of complete rulers with length n.

Terms

a(0) =1a(1) =1a(2) =1a(3) =3a(4) =4a(5) =9a(6) =17a(7) =33a(8) =63a(9) =128a(10) =248a(11) =495a(12) =988a(13) =1969a(14) =3911a(15) =7857a(16) =15635a(17) =31304a(18) =62732a(19) =125501a(20) =250793a(21) =503203a(22) =1006339a(23) =2014992a(24) =4035985a(25) =8080448a(26) =16169267a(27) =32397761a(28) =64826967a(29) =129774838