Numbers k such that k^2 divides 5^k-1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =6a(4) =12a(5) =42a(6) =52a(7) =84a(8) =156a(9) =186a(10) =372a(11) =1092a(12) =1218a(13) =1302a(14) =1806a(15) =2436a(16) =2604a(17) =2756a(18) =3612a(19) =4836a(20) =5334a(21) =7212a(22) =8268a(23) =10668a(24) =12324a(25) =15918a(26) =18858a(27) =24492a(28) =31668a(29) =31836