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 A328020 #30 Oct 14 2019 01:26:52 %S A328020 1,1,2,22,515,56734,19846102,23437350133 %N A328020 Number of distinct tilings of an n X n square with free n-polyominoes. %H A328020 Jeff Bowermaster, <a href="/A328020/a328020.png">Illustration of a(1)..a(4)</a> %H A328020 Jeff Bowermaster, <a href="/A328020/a328020_1.png">Illustration of a(5)</a> %H A328020 Code Golf Stack Exchange, <a href="https://codegolf.stackexchange.com/q/194056/53884">Number of distinct tilings of an n X n square with free n-polyominoes</a> %Y A328020 Cf. A172477, A268427, A291806. %K A328020 nonn,hard,more,nice %O A328020 1,3 %A A328020 _Jeff Bowermaster_, Oct 01 2019 %E A328020 a(7) from _Peter Kagey_, Oct 10 2019, based on the Stack Exchange link. %E A328020 a(8) from _Christian Sievers_, Oct 13 2019, based on the Stack Exchange link.