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 A230031 #48 Mar 26 2025 16:23:18 %S A230031 1,1,1,1,0,1,1,0,0,1,1,0,1,0,1,1,1,0,0,1,1,1,0,4,0,4,0,1,1,0,0,23,23, %T A230031 0,0,1,1,0,9,0,117,0,9,0,1,1,1,0,0,454,454,0,0,1,1,1,0,25,0,2003,0, %U A230031 2003,0,25,0,1,1,0,0,997,9157,0,0,9157,997,0,0,1 %N A230031 Number A(n,k) of tilings of a k X n rectangle using tetrominoes of any shape; square array A(n,k), n>=0, k>=0, read by antidiagonals. %H A230031 Liang Kai, <a href="/A230031/b230031.txt">Antidiagonals n = 0..27, flattened</a> (Antidiagonals n = 0..20 from Alois P. Heinz) %H A230031 S. Butler, J. Ekstrand, S. Osborne, <a href="/A230031/a230031.pdf">TETRIS Tiling</a>, AMS Spring Central Sectional, Iowa State University, April 27-28 2013 %H A230031 R. S. Harris, <a href="http://www.bumblebeagle.org/polyominoes/tilingcounting">Counting Polyomino Tilings</a> %H A230031 Liang Kai, <a href="https://arxiv.org/abs/2503.17698">Solving tiling enumeration problems by tensor network contractions</a>, arXiv:2503.17698 [math.CO], 2025. %H A230031 Wikipedia, <a href="https://en.wikipedia.org/wiki/Tetris">Tetris</a> %H A230031 Wikipedia, <a href="https://en.wikipedia.org/wiki/Tetromino">Tetromino</a> %F A230031 A(n,k) = 0 <=> n*k mod 4 > 0. %e A230031 A(4,2) = A(2,4) = 4: %e A230031 ._______. ._______. ._______. ._______. %e A230031 | | | |_______| | |___. | | .___| | %e A230031 |___|___| |_______| |_____|_| |_|_____|. %e A230031 Square array A(n,k) begins: %e A230031 1, 1, 1, 1, 1, 1, 1, 1, 1, ... %e A230031 1, 0, 0, 0, 1, 0, 0, 0, 1, ... %e A230031 1, 0, 1, 0, 4, 0, 9, 0, 25, ... %e A230031 1, 0, 0, 0, 23, 0, 0, 0, 997, ... %e A230031 1, 1, 4, 23, 117, 454, 2003, 9157, 40899, ... %e A230031 1, 0, 0, 0, 454, 0, 0, 0, 800290, ... %e A230031 1, 0, 9, 0, 2003, 0, 178939, 0, 22483347, ... %e A230031 1, 0, 0, 0, 9157, 0, 0, 0, 657253434, ... %e A230031 1, 1, 25, 997, 40899, 800290, 22483347, 657253434, 19077209438, ... %Y A230031 Columns (or rows) include: A000012, A007598, A232757, A174248, A232758, A232684, A232759, A232698, A247113, A232722. %Y A230031 Bisection of main diagonal (even part) gives A263425. %Y A230031 Cf. A099390, A233320, A233427. %K A230031 nonn,tabl %O A230031 0,24 %A A230031 _Alois P. Heinz_, Nov 29 2013