Numbers k such that k^2 divides 3^k-1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =20a(4) =220a(5) =1220a(6) =2420a(7) =5060a(8) =13420a(9) =14740a(10) =23620a(11) =55660a(12) =145420a(13) =147620a(14) =162140a(15) =237820a(16) =259820a(17) =290620a(18) =308660a(19) =339020a(20) =447740a(21) =847220a(22) =899140a(23) =1210220a(24) =1440820a(25) =1599620a(26) =1759340a(27) =2332660a(28) =2616020a(29) =2858020