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 A219952 #22 Mar 30 2025 10:57:01 %S A219952 1,0,1,0,6,0,545,5504,652036,44013568,11112714624,3517475475328, %T A219952 2781543486427548,3568483481372543360,9829161878198755474915, %U A219952 48599777948701165162242560,484370819140388708451108625276,9036085159101926537420075859958528 %N A219952 Number of tilings of an n X n square using right trominoes and 2 X 2 tiles. %H A219952 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 A219952 a(4) = 6, because there are 6 tilings of a 4 X 4 square using right trominoes and 2 X 2 tiles: %e A219952 .___.___. .___.___. .___.___. .___.___. .___.___. .___.___. %e A219952 | . | . | | ._|_. | | ._| . | | ._|_. | | ._|_. | | . |_. | %e A219952 |___|___| |_| . |_| |_| |___| |_| ._|_| |_|_. |_| |___| |_| %e A219952 | . | . | | |___| | | |___| | | |_| . | | . |_| | | |___| | %e A219952 |___|___| |___|___| |___|___| |___|___| |___|___| |___|___| %Y A219952 Main diagonal of A219946. %Y A219952 Cf. A233807. %K A219952 nonn %O A219952 0,5 %A A219952 _Alois P. Heinz_, Dec 01 2012 %E A219952 a(15)-a(16) from _Alois P. Heinz_, Sep 24 2014 %E A219952 a(17) from _Alois P. Heinz_, Nov 18 2018