%I #22 Nov 05 2018 10:38:38
%S 1,2,4,8,10,172,296,332,410,872,1048,1070,1544,2830,3470,7486,9196,
%T 22184,90892,121174,299816,575206,885112,1329388,1386430,2518994,
%U 4167272,5600212,8475016,9180370,12348446,18483076,19185890,20806274,28984094,37114141
%N Positive integers k such that 13^k == 9 (mod k).
%C For k > 9 in this sequence, A116609(k) = 9. - _Iain Fox_, Nov 20 2017
%H Max Alekseyev, <a href="/A116636/b116636.txt">Table of n, a(n) for n = 1..112</a>
%t Join[{1, 2, 4, 8}, Select[Range[1, 9000], Mod[13^#, #] == 9 &]] (* _G. C. Greubel_, Nov 19 2017 *)
%o (PARI) isok(n) = Mod(13, n)^n == 9; \\ _Michel Marcus_, Nov 19 2017
%Y 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 Cf. A116609.
%K nonn
%O 1,2
%A _Zak Seidov_, Feb 19 2006
%E More terms from _Ryan Propper_, Nov 05 2006
%E Terms 1,2,4,8 prepended by _Max Alekseyev_, Jun 28 2011