Numbers k such that k^2 divides 9^k - 1.

Terms

a(0) =1a(1) =2a(2) =4a(3) =8a(4) =10a(5) =20a(6) =40a(7) =110a(8) =136a(9) =164a(10) =220a(11) =328a(12) =440a(13) =610a(14) =680a(15) =820a(16) =1210a(17) =1220a(18) =1544a(19) =1640a(20) =2420a(21) =2440a(22) =2530a(23) =4840a(24) =5060a(25) =5576a(26) =6710a(27) =7370a(28) =7480a(29) =7720