A128123 Numbers k such that 2^k == 10 (mod k).

1, 2, 6, 18, 16666, 262134, 4048124214, 24430928839, 243293052886, 41293676570106, 3935632929857549

Offset

1,2

Comments

Some larger terms: 266895924489780149, 2335291686841914329, 18494453435532853111

Links

Table of n, a(n) for n=1..11.

Joe K. Crump, 2^n mod n

Mathematica

m = 10; Join[Select[Range[m], Divisible[2^# - m, #] &],
Select[Range[m + 1, 10^6], PowerMod[2, #, #] == m &]] (* Robert Price, Oct 08 2018 *)

Crossrefs

Cf. A015910, A036236, A050259 (numbers k such that 2^k == 3 (mod k)), A033981, A051447, A033982, A051446, A033983, A128121, A128122, A128124, A128125, A128126.

Sequence in context: A240643 A262971 A253380 * A227884 A186769 A213400

Adjacent sequences: A128120 A128121 A128122 * A128124 A128125 A128126

Keyword

hard,more,nonn

Author

Alexander Adamchuk, Feb 15 2007

Extensions

1, 2 and 6 added by N. J. A. Sloane, Apr 23 2007

Missing terms a(9)-a(10) added by Max Alekseyev, Dec 16 2013

a(11) from Max Alekseyev, Sep 27 2016

Status

approved