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 A245620 #25 Apr 26 2023 07:00:08 %S A245620 1,0,0,0,1,0,0,1,1,0,2,2,3,4,7,10,17,28,47,69 %N A245620 Number of unitary polyominoes with n cells. A unitary polyomino is a polyomino whose edges all have length 1. %C A245620 If a unitary polyomino is colored in checks, all cells on each boundary have the same color. This characterizes unitary polyominoes. %H A245620 Alberto Del Lungo, Massimo Mirolli, Renzo Pinzani, and Simone Rinaldi, <a href="https://doi.org/10.46298/dmtcs.2298">A Bijection for Directed Polyominoes</a>, Discrete Mathematics and Theoretical Computer Science Proceedings, AA (2001), 133-144. %H A245620 George Sicherman, <a href="https://sicherman.net/nunitary/nunitary.html">Catalogue of Unitary Polyominoes</a> %e A245620 The monomino (a single square) is unitary. The domino, trominoes, and tetrominoes are not. The X pentomino is unitary; the other pentominoes are not. %Y A245620 Cf. A000105 (number of free polyominoes with n cells). %Y A245620 Cf. A245660 (unitary polyominoes without holes). %K A245620 nonn,hard,more,nice %O A245620 1,11 %A A245620 _George Sicherman_, Jul 27 2014