a(n) = |{m : multiplicative order of 2 mod m = n}|.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =1a(5) =3a(6) =1a(7) =4a(8) =2a(9) =5a(10) =3a(11) =16a(12) =1a(13) =5a(14) =5a(15) =8a(16) =1a(17) =24a(18) =1a(19) =38a(20) =9a(21) =11a(22) =3a(23) =68a(24) =6a(25) =5a(26) =4a(27) =54a(28) =7a(29) =79