A127101 Numbers k such that k^2 divides 9^k - 1.

1, 2, 4, 8, 10, 20, 40, 110, 136, 164, 220, 328, 440, 610, 680, 820, 1210, 1220, 1544, 1640, 2420, 2440, 2530, 4840, 5060, 5576, 6710, 7370, 7480, 7720, 9020, 10120, 11810, 13420, 13612, 14008, 14740, 18040, 18632, 19580

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..3000 (terms 1..56 from R. J. Mathar)

Mathematica

Select[Range[20000], IntegerQ[(PowerMod[9, #, #^2 ]-1)/#^2 ]&]

Prog

(PARI) is(k) = Mod(9, k^2)^k == 1; \\ Amiram Eldar, May 21 2024

Crossrefs

Subset of A068382 (numbers k such that k divides 9^k - 1).

Cf. A127100, A127102, A127103, A123104, A127105, A127106, A127107, A127092.

Sequence in context: A177909 A259386 A004655 * A308832 A124849 A056654

Adjacent sequences: A127098 A127099 A127100 * A127102 A127103 A127104

Keyword

nonn,changed

Author

Alexander Adamchuk, Jan 05 2007

Status

approved