This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A116636 #24 Jul 06 2025 15:27:01
%S A116636 1,2,4,8,10,172,296,332,410,872,1048,1070,1544,2830,3470,7486,9196,
%T A116636 22184,90892,121174,299816,575206,885112,1329388,1386430,2518994,
%U A116636 4167272,5600212,8475016,9180370,12348446,18483076,19185890,20806274,28984094,37114141
%N A116636 Positive integers k such that 13^k == 9 (mod k).
%C A116636 For k > 9 in this sequence, A116609(k) = 9. - _Iain Fox_, Nov 20 2017
%H A116636 Max Alekseyev, <a href="/A116636/b116636.txt">Table of n, a(n) for n = 1..112</a>
%t A116636 Join[{1, 2, 4, 8}, Select[Range[1, 9000], Mod[13^#, #] == 9 &]] (* _G. C. Greubel_, Nov 19 2017 *)
%t A116636 Join[{1,2,4,8},Select[Range[38*10^6],PowerMod[13,#,#]==9&]] (* _Harvey P. Dale_, Jul 06 2025 *)
%o A116636 (PARI) isok(n) = Mod(13, n)^n == 9; \\ _Michel Marcus_, Nov 19 2017
%Y A116636 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).
%Y A116636 Cf. A116609.
%K A116636 nonn
%O A116636 1,2
%A A116636 _Zak Seidov_, Feb 19 2006
%E A116636 More terms from _Ryan Propper_, Nov 05 2006
%E A116636 Terms 1,2,4,8 prepended by _Max Alekseyev_, Jun 28 2011