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 A336489 #8 Jul 25 2020 14:00:39 %S A336489 0,1,2,8,18,32,50,102,126,198,286,390,510,742,878,1130,1414,1770,2166, %T A336489 2778,3186,3858,4594,5342,6146,7342,8294,9662,11134,12710,14390,16582, %U A336489 18226,20518,22946,25662,28530,32270,35250,38862,42650,46614,50754,55990,60730 %N A336489 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 three lines cross. %H A336489 Lars Blomberg, <a href="/A336489/b336489.txt">Table of n, a(n) for n = 1..500</a> %Y A336489 Cf. A334701, A336490, A336491. %K A336489 nonn %O A336489 1,3 %A A336489 _Lars Blomberg_, Jul 25 2020