Numbers k such that 5^k == -1 (mod k-1).

Terms

a(0) =2a(1) =3a(2) =7a(3) =14a(4) =15a(5) =175a(6) =855a(7) =2695a(8) =78127a(9) =103974a(10) =106695a(11) =121975a(12) =420210a(13) =487375a(14) =1299375a(15) =2174655a(16) =3895095a(17) =4151455a(18) =5842215a(19) =5951130a(20) =6508335a(21) =10637055a(22) =20117895a(23) =24482958a(24) =31999695a(25) =32282054a(26) =32620203a(27) =32872455a(28) =34258455