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 A337828 #19 Sep 26 2020 11:28:19 %S A337828 5,101,62501,1020101,31562501,139476101,637562501,789062501,985502501, %T A337828 2656262501,7455062501,19726562501,53662562501 %N A337828 Odd integers k such that 3^((k-1)/2) + 1 == 0 (mod k*(k-1)/2). %C A337828 Computed terms are prime. %t A337828 Select[Range[3, 3*10^7, 2], PowerMod[3, (# - 1)/2, (t = #*(# - 1)/2)] == t - 1 &] (* _Amiram Eldar_, Sep 24 2020 *) %Y A337828 Cf. A337818. %K A337828 nonn,more %O A337828 1,1 %A A337828 _Benoit Cloitre_, Sep 24 2020 %E A337828 a(7)-a(13) from _Amiram Eldar_, Sep 25 2020