Numbers k such that k divides 4^k - 1.

Terms

a(0) =1a(1) =3a(2) =9a(3) =21a(4) =27a(5) =63a(6) =81a(7) =147a(8) =171a(9) =189a(10) =243a(11) =441a(12) =513a(13) =567a(14) =657a(15) =729a(16) =903a(17) =1029a(18) =1197a(19) =1323a(20) =1539a(21) =1701a(22) =1971a(23) =2187a(24) =2667a(25) =2709a(26) =3087a(27) =3249a(28) =3591a(29) =3969