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 A366020 #7 Sep 29 2023 08:27:39 %S A366020 1,1,2,3,8,13,36,76,201,476,1218,2952,7282,17566,42657,102931,249119 %N A366020 Number of polyominoes in which every cell has coprime coordinates. %e A366020 For n = 9, the only polyomino from A294151 which does not belong to this sequence is the following, because it has always one cell whose coordinates are both divisible by 3 : %e A366020 |#|#|#| %e A366020 |#| |#| |#| %e A366020 |#|#|#| %Y A366020 Cf. A000105, A347521, A294151. %K A366020 nonn,more,hard %O A366020 1,3 %A A366020 _Ludovic Schwob_, Sep 26 2023