Number of distinct length-n necklaces on a size-2 alphabet.

Terms

a(0) =2a(1) =1a(2) =2a(3) =1a(4) =2a(5) =3a(6) =4a(7) =2a(8) =4a(9) =3a(10) =6a(11) =9a(12) =12a(13) =20a(14) =32a(15) =16a(16) =32a(17) =36a(18) =68a(19) =57a(20) =138a(21) =123a(22) =252a(23) =378a(24) =504a(25) =420a(26) =1296a(27) =1520a(28) =2176a(29) =2816