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 A277350 #18 Oct 18 2016 10:12:41 %S A277350 1,15853,5520343,111966563,2232207889,5551501871 %N A277350 Positive integers n such that 5^n == 6 (mod n). %C A277350 No other terms below 10^15. - _Max Alekseyev_, Oct 18 2016 %o A277350 (PARI) isok(n) = Mod(5, n)^n == 6; \\ _Michel Marcus_, Oct 10 2016 %Y A277350 Cf. Solutions to 5^n == k (mod n): A277348 (k=-6), A015891 (k=-5), A123047 (k=-4), A123052 (k=-3), A123062 (k=-2), A015951 (k=-1), A067946 (k=1), A124246 (k=2), A123061 (k=3), A125949 (k=4), A123091 (k=5), this sequence (k=6). %K A277350 nonn,hard,more %O A277350 1,2 %A A277350 _Seiichi Manyama_, Oct 10 2016