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 A015974 #10 Aug 21 2021 22:19:12 %S A015974 205,1025,2525,5125,8405,12625,25625,42025,63125,103525,128125,168305, %T A015974 202525,210125,255025,315625,344605,517625,640625,841525,875125, %U A015974 1012625,1050625,1275125,1578125,1723025,2042725,2084645 %N A015974 Numbers k that divide 4^k + 1, k not a power of 5. %Y A015974 Cf. A015950. %K A015974 nonn %O A015974 1,1 %A A015974 _Robert G. Wilson v_