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 A277554 #10 Oct 20 2016 06:03:42 %S A277554 1,2,46,2227,6684830083,12827743861,151652531182,155657642297, %T A277554 3102126273955,11006109076099,50473807426174,172794904196354 %N A277554 Positive integers n such that 7^n == 3 (mod n). %C A277554 No other terms below 10^15. %o A277554 (PARI) isok(n) = Mod(7, n)^n == 3; \\ _Michel Marcus_, Oct 20 2016 %Y A277554 Cf. A066438, A277126. %Y A277554 Cf. Solutions to 7^n == k (mod n): A277371 (k=-3), A277370 (k=-2), A015954 (k=-1), A067947 (k=1), A277401 (k=2). %Y A277554 Cf. Solutions to b^n == 3 (mod n): A050259 (b=2), A130422 (b=4), A123061 (b=5), A116629 (b=13). %K A277554 nonn,hard,more %O A277554 1,2 %A A277554 _Max Alekseyev_, Oct 19 2016