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 A220061 #19 Mar 30 2025 10:56:19 %S A220061 1,1,5,39,2023,249651,128938297,207866584389,1208344842789831, %T A220061 23649239068131551559,1609120545126107661426575, %U A220061 375082120094104660413783094451,301522432794951154854984388046484015,833441700776362178606942848178200903068675,7931715551857283775957120938092133944383839378911 %N A220061 Number of tilings of an n X n square using right trominoes and 1 X 1 tiles. %H A220061 Alois P. Heinz, <a href="/A220061/b220061.txt">Table of n, a(n) for n = 0..16</a> %H A220061 Kai Liang, <a href="https://arxiv.org/abs/2503.17698">Solving tiling enumeration problems by tensor network contractions</a>, arXiv:2503.17698 [math.CO], 2025. See p. 25, Table 4. %e A220061 a(2) = 5, because there are 5 tilings of a 2 X 2 square using right trominoes and 1 X 1 tiles: %e A220061 ._._. ._._. .___. .___. ._._. %e A220061 |_|_| | |_| | ._| |_. | |_| | %e A220061 |_|_| |___| |_|_| |_|_| |___| %Y A220061 Main diagonal of A220054. %Y A220061 Cf. A233807. %K A220061 nonn %O A220061 0,3 %A A220061 _Alois P. Heinz_, Dec 03 2012