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

Table of n, a(n) for n=1..42.

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 *)

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