A116632 Positive integers n such that 13^n == 7 (mod n).

1, 2, 3, 6, 15, 75, 219, 1335, 3246, 4975, 5475, 7775, 8922, 28614, 67675, 69998, 103135, 313609, 548983, 624193, 6539595, 13193562, 26383395, 111892866, 315953675, 5330142066, 33738816835, 66899423586, 336966134829, 645835313441, 742199683475, 1244107219389, 10187548490537, 760354210440662

Offset: 1

Author

Zak Seidov, Feb 19 2006

Keywords

• nonn

Comments

No other terms below 10^15. - Max Alekseyev, Oct 30 2018

Some larger terms: 6584692157923407917184426, 3226231185229904054184099310127719809, 30643479515551752620928357020812679775, 5890087594520845596744547263586007316572563275. - Max Alekseyev, Oct 30 2018

Crossrefs

Cf. A116609, A116611, A116620, A116621, A116622, A116629, A116630, A116631.

Programs

Mathematica

Join[{1, 2, 3, 6}, Select[Range[1, 9000], Mod[13^#, #] == 7 &]] (* G. C. Greubel, Nov 19 2017 *)
Join[{1, 2, 3, 6}, Select[Range[10000000], PowerMod[13, #, #] == 7 &]] (* Robert Price, Apr 10 2020 *)

PARI

isok(n) = Mod(13, n)^n == 7; \\ Michel Marcus, Nov 19 2017

Extensions

More terms from Ryan Propper, Mar 30 2007

Terms 1,2,3,6 prepended and a(27)-a(34) added by Max Alekseyev, Jun 30 2011, Oct 30 2018