Numbers k such that 3^k == -1 (mod k-1).

Terms

a(0) =2a(1) =3a(2) =5a(3) =6a(4) =15a(5) =245a(6) =366a(7) =435a(8) =855a(9) =2295a(10) =3795a(11) =5967a(12) =7875a(13) =10878a(14) =26475a(15) =33915a(16) =117615a(17) =188775a(18) =231435a(19) =284355a(20) =487635a(21) =501039a(22) =589155a(23) =593775a(24) =621675a(25) =755595a(26) =1255815a(27) =1306935a(28) =1642095a(29) =1911195