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 A308891 #7 Jul 01 2019 23:05:11 %S A308891 1,2,3,4,21,26,31,36,37,38,41,42,43,48,49,50,55,56,57,64,66,71,80,89, %T A308891 95,96,111,113,115,116,122,124,126,127,133,135,138,139,142,144,145, %U A308891 146,148,150,151,153,155,156,157,163,166,168,169,170,176,179,181,182,183,196,198,209,215,224 %N A308891 Positions of 0's on the spiral defined in A308890. %C A308891 Add 1 to the terms of A308885. %Y A308891 Cf. A308884-A308895. %K A308891 nonn %O A308891 1,2 %A A308891 _N. J. A. Sloane_, Jul 01 2019