A128395 Numbers k such that k^2 divides 15^k-1.

1, 2, 4, 7, 8, 14, 16, 28, 56, 112, 136, 272, 452, 812, 904, 952, 1624, 1808, 1904, 3164, 3248, 6328, 11912, 12656, 15368, 18632, 23824, 27608, 30736, 37264, 47908, 55216, 60248, 83384, 91756, 95816, 102604, 107576, 113936, 120496, 130424, 166768

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..640

Mathematica

a={1}; For[n=1, n<200000, n++, If[PowerMod[15, n, n^2]==1, AppendTo[a, n]]]; a (* Stefan Steinerberger, Jun 10 2007 *)
Join[{1}, Select[Range[167000], PowerMod[15, #, #^2]==1&]] (* Harvey P. Dale, Sep 14 2020 *)

Prog

(PARI) is(k) = Mod(15, k^2)^k == 1; \\ Amiram Eldar, May 21 2024

Crossrefs

Cf. A127103, A127104, A127105, A127106, A127107, A127102, A127101, A127100, A127092, A128405, A128393, A128395, A128396, A128397, A128398, A128399, A128400, A128401, A128402, A128403, A128404.

Sequence in context: A018645 A177915 A018289 * A018740 A281275 A015893

Adjacent sequences: A128392 A128393 A128394 * A128396 A128397 A128398

Keyword

nonn,less

Author

Alexander Adamchuk, Mar 01 2007

Extensions

More terms from Stefan Steinerberger, Jun 10 2007

Status

approved