Nonprimes k such that 7^k == 7 (mod k).

Terms

a(0) =1a(1) =6a(2) =14a(3) =21a(4) =25a(5) =42a(6) =105a(7) =133a(8) =231a(9) =301a(10) =325a(11) =525a(12) =561a(13) =703a(14) =817a(15) =1105a(16) =1729a(17) =1825a(18) =2101a(19) =2353a(20) =2465a(21) =2821a(22) =3277a(23) =3325a(24) =3486a(25) =3913a(26) =4011a(27) =4525a(28) =4825a(29) =5565