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 A325301 #14 Dec 31 2020 11:11:15 %S A325301 12,21,36,51,63,84,96,117,138,165,177,204,216,240,273,306,318,351,363 %N A325301 a(n) is the number of edges of the stepped pyramid with n levels described in A245092. %C A325301 To calculate a(n) consider that levels greater than n do not exist. %H A325301 Omar E. Pol, <a href="http://www.polprimos.com/imagenespub/polpyr05.jpg">Perspective view of the pyramid (first 16 levels)</a> %F A325301 a(n) = A325300(n) + A325302(n) - 2 (Euler's formula). %e A325301 For n = 1 the first level of the stepped pyramid (starting from the top) is a cube, and a cube has 12 edges, so a(1) = 12. %Y A325301 Cf. A325300 (number of faces), A325302 (number of vertices). %Y A325301 Cf. A196020, A235791, A236104, A237270, A237271, A237591, A237593, A245092, A262626, A294848, A294849, A317109, A323648. %K A325301 nonn,more %O A325301 1,1 %A A325301 _Omar E. Pol_, Apr 16 2019