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 A116620 #16 Apr 10 2020 22:09:48
%S A116620 1,3,9,74853,1275039,27181907,31261887,989255061,4813809711,
%T A116620 3187842157567,313768710194691
%N A116620 Positive integers n such that 13^n == 10 (mod n).
%C A116620 No other terms below 10^15. - _Max Alekseyev_, Nov 06 2018
%C A116620 9909932321420413420533943 is a term. - _Max Alekseyev_, Jun 29 2011
%t A116620 Join[{1, 3, 9}, Select[Range[2000000], PowerMod[13, #, #] == 10 &]] (* _Robert Price_, Apr 10 2020 *)
%Y A116620 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), A116636 (k=9), this sequence (k=10), A116638 (k=11), A116639 (k=15).
%Y A116620 Cf. A116609.
%K A116620 more,nonn
%O A116620 1,2
%A A116620 _Zak Seidov_, Feb 19 2006
%E A116620 More terms from _Ryan Propper_, Jun 12 2006
%E A116620 Terms 1,3,9 prepended and a(10)-a(11) added by _Max Alekseyev_, Jun 29 2011, Nov 06 2018