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 A339739 #39 Jun 15 2024 15:25:42 %S A339739 0,0,0,1,4,11,30,78,205,546,1455,4062,11192,31889,88487,254594,710683, %T A339739 2047705,5711439,16455169,45894868,132118562,368149344,1059171430, %U A339739 2950384277,8484556353 %N A339739 a(n) gives the number of squares in the n-th iteration of the Harter-Heighway dragon. %C A339739 a(n) >= A003230(n-4) for n >= 4, and a(n) > A003230(n-4) for n >= 7. %H A339739 Code Golf Stack Exchange user Domenico Modica, <a href="https://codegolf.stackexchange.com/q/216919/53884">Eye test - How many squares are in this picture?</a> %H A339739 Wikipedia, <a href="https://en.wikipedia.org/wiki/Dragon_curve#Heighway_dragon">Dragon Curve</a> %e A339739 For n = 5, the fifth iteration of the Harter-Heighway dragon has a(5) = 4 squares, as illustrated below. All of the squares are 1 X 1. %e A339739 *---* %e A339739 | | %e A339739 *---* * %e A339739 | %e A339739 *---* %e A339739 | %e A339739 *---*---* *---* *---* %e A339739 | | | | | | | %e A339739 *---* *---*---*---* *---* %e A339739 | | | %e A339739 *---*---* *---* %e A339739 | | %e A339739 *---* %e A339739 For n = 7, the seventh iteration of the Harter-Heighway dragon has a(7) = 30 squares, as illustrated below. It contains A003230(7) = 28 1 X 1 squares and two 2 X 2 squares. %e A339739 _ _ %e A339739 |_|_| |_ %e A339739 _ _| _| %e A339739 |_|_|_ %e A339739 |_|_| %e A339739 |_ _ _ _ %e A339739 _ _|_|_| _|_| _|_| %e A339739 |_|_|_|_|_ _|_|_ _|_|_ _ %e A339739 |_| |_| |_|_|_|_|_| |_| |_|_| %e A339739 |_|_|_|_ |_ %e A339739 _ _|_| |_| _| %e A339739 |_|_|_|_ |_| %e A339739 |_| |_| %Y A339739 A003230 gives the number of 1 X 1 squares. %K A339739 nonn,more %O A339739 1,5 %A A339739 _Peter Kagey_, Jan 05 2021 %E A339739 a(17)-a(26) from _Bert Dobbelaere_, Jun 15 2024