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 A337132 #15 Dec 05 2020 04:34:41 %S A337132 1,4,4,4,12,4,4,12,4,4,12,12,12,36,4,4,12,4,4,12,12,12,36,4,4,12,4,4, %T A337132 12,12,12,36,12,12,36,12,12,36,36,36,108,4,4,12,4,4,12,12,12,36,4,4, %U A337132 12,4,4,12,12,12,36,12,12,36,12,12,36,36,36,108,4,4,12 %N A337132 a(n) is the number of squares at distance n from the central square of a Vicsek fractal. %C A337132 For symmetry reasons, a(n) is a multiple of 4 for any n > 0. %H A337132 Rémy Sigrist, <a href="/A337132/b337132.txt">Table of n, a(n) for n = 0..6561</a> %H A337132 Rémy Sigrist, <a href="/A337132/a337132.png">Illustration of initial terms</a> %H A337132 Rémy Sigrist, <a href="/A337132/a337132.gp.txt">PARI program for A337132</a> %H A337132 Wikipedia, <a href="https://en.wikipedia.org/wiki/Vicsek_fractal">Vicsek fractal</a> %F A337132 a(n) = 4 iff n belongs to A153775. %o A337132 (PARI) See Links section. %Y A337132 See A337018 for similar sequences. %Y A337132 Cf. A153775. %K A337132 nonn %O A337132 0,2 %A A337132 _Rémy Sigrist_, Nov 21 2020