A116636 Positive integers k such that 13^k == 9 (mod k).

1, 2, 4, 8, 10, 172, 296, 332, 410, 872, 1048, 1070, 1544, 2830, 3470, 7486, 9196, 22184, 90892, 121174, 299816, 575206, 885112, 1329388, 1386430, 2518994, 4167272, 5600212, 8475016, 9180370, 12348446, 18483076, 19185890, 20806274, 28984094, 37114141

Offset: 1

Author

Zak Seidov, Feb 19 2006

Keywords

• nonn

Comments

For k > 9 in this sequence, A116609(k) = 9. - Iain Fox, Nov 20 2017

Links

• Max Alekseyev, Table of n, a(n) for n = 1..112

Crossrefs

Solutions to 13^n == k (mod n): A001022 (k=0), A015963 (k=-1), A116621 (k=1), A116622 (k=2), A116629 (k=3), A116630 (k=4), A116611 (k=5), A116631 (k=6), A116632 (k=7), A295532 (k=8), this sequence (k=9), A116620 (k=10), A116638 (k=11), A116639 (k=15).

Cf. A116609.

Programs

Mathematica

Join[{1, 2, 4, 8}, Select[Range[1, 9000], Mod[13^#, #] == 9 &]] (* G. C. Greubel, Nov 19 2017 *)
Join[{1,2,4,8},Select[Range[38*10^6],PowerMod[13,#,#]==9&]] (* Harvey P. Dale, Jul 06 2025 *)

PARI

isok(n) = Mod(13, n)^n == 9; \\ Michel Marcus, Nov 19 2017

Extensions

More terms from Ryan Propper, Nov 05 2006

Terms 1,2,4,8 prepended by Max Alekseyev, Jun 28 2011