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 A300694 #13 Apr 03 2018 10:13:18 %S A300694 0,1,13,139,1605,20741 %N A300694 a(n) = number of edges in a cocoon concertina n-cube. %C A300694 n-place formulas in first-order logic like Ax Ey P(x, y) or Ex P(x, x) can be ordered by implication. This Hasse diagram has A300696(n) vertices and a(n) edges. %C A300694 The corresponding sequence for convex concertina n-cubes is A300693. %H A300694 Tilman Piesk, <a href="https://en.wikiversity.org/wiki/Formulas_in_predicate_logic">Formulas in predicate logic</a> (Wikiversity) %H A300694 Tilman Piesk, <a href="https://commons.wikimedia.org/wiki/File:Cocoon_concertina_square_graph.svg">Image of a cocoon concertina square</a> with 13 edges %H A300694 Tilman Piesk, <a href="https://github.com/watchduck/concertina_hypercubes/tree/master/computed_results/cocoon/hasse">Lists of edges</a> for n=2..5 %H A300694 Tilman Piesk, <a href="https://github.com/watchduck/concertina_hypercubes/blob/master/cocoon.py">Python code used to generate the sequence</a> %e A300694 The cocoon concertina square has the A300693(2) = 6 outer and 7 inner edges, giving a(n) = 13 in total. %Y A300694 Cf. A300696, A300693. %K A300694 nonn,more %O A300694 0,3 %A A300694 _Tilman Piesk_, Mar 24 2018