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 A270071 #10 Apr 25 2025 21:04:26 %S A270071 1,1,5,93,7517,2501946,3473827027,19823918037604,466326405037190729, %T A270071 45283517791861200639757,18137923612752525595542410804, %U A270071 29967243098804386765778629249653298,204247259656641635611144023845458294818885 %N A270071 Number of tilings of an n X n square using monominoes and trominoes of any shape. %H A270071 Liang Kai, <a href="/A270071/b270071.txt">Table of n, a(n) for n = 0..17</a> %H A270071 Wikipedia, <a href="https://en.wikipedia.org/wiki/Tromino">Tromino</a> %Y A270071 Main diagonal of A270061. %K A270071 nonn %O A270071 0,3 %A A270071 _Alois P. Heinz_, Mar 09 2016