Numbers k such that k^2 divides 7^k-1.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =6a(5) =8a(6) =12a(7) =20a(8) =24a(9) =40a(10) =57a(11) =60a(12) =100a(13) =114a(14) =120a(15) =156a(16) =200a(17) =220a(18) =228a(19) =258a(20) =300a(21) =312a(22) =440a(23) =456a(24) =516a(25) =600a(26) =660a(27) =780a(28) =1032a(29) =1100