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 A336490 #14 Oct 01 2020 04:04:47 %S A336490 0,0,1,2,2,10,22,18,32,62,100,118,136,154,274,346,426,554,698,726,884, %T A336490 1058,1248,1454,1784,2146,2714,2978,3250,3722,4226,4490,5104,5758, %U A336490 6674,7350,8058,8798,10062,11238,12478,14046,15702,16526,18016,19570,21188,22870 %N A336490 Consider the figure made up of a row of n adjacent congruent rectangles, with diagonals of all possible rectangles drawn; a(n) is the number of interior vertices where exactly four lines cross. %H A336490 Lars Blomberg, <a href="/A336490/b336490.txt">Table of n, a(n) for n = 1..500</a> %Y A336490 Cf. A334701, A336489, A336491. %K A336490 nonn %O A336490 1,4 %A A336490 _Lars Blomberg_, Jul 25 2020