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 A336491 #7 Jul 25 2020 14:00:53 %S A336491 0,0,0,1,2,2,2,12,26,20,10,38,74,118,102,114,126,178,238,306,382,466, %T A336491 558,762,774,778,774,942,1126,1326,1542,1910,2310,2742,2762,3070,3394, %U A336491 3734,4090,4294,4498,4966,5458,6434,6910,7402,7910,8834,9806,10410,11030 %N A336491 Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) = number of interior vertices where exactly five lines cross. %H A336491 Lars Blomberg, <a href="/A336491/b336491.txt">Table of n, a(n) for n = 1..500</a> %Y A336491 Cf. A334701, A336489, A336490. %K A336491 nonn %O A336491 1,5 %A A336491 _Lars Blomberg_, Jul 25 2020