Numbers k such that 9^k == -1 (mod k-1).

Terms

a(0) =2a(1) =3a(2) =11a(3) =42a(4) =147a(5) =13818a(6) =21450a(7) =27594a(8) =41370a(9) =55011a(10) =126291a(11) =265722a(12) =417123a(13) =1315635a(14) =3994571a(15) =5704611a(16) =6860490a(17) =9298842a(18) =13941354a(19) =14349027a(20) =17658578a(21) =20382810a(22) =26557874a(23) =27841338a(24) =69831363a(25) =86550090a(26) =113272170a(27) =130457571a(28) =163013235a(29) =192688650