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 A365862 #30 Oct 30 2023 13:05:08 %S A365862 1,0,0,0,2,0,20,54,6464 %N A365862 Number of 4-fold rotationally symmetric pentomino tilings of the 5n X 5n square such that no two tiles can be replaced with two pentomominoes in a new configuration. %C A365862 a(n) is even for all n > 0 since no pentomino tiling can have both rotation and reflection symmetry. %H A365862 Jamie Tucker-Foltz, <a href="https://arxiv.org/abs/2307.15996">Locked Polyomino Tilings</a>, arXiv:2307.15996 [math.CO], 2023. %H A365862 Jamie Tucker-Foltz, <a href="https://github.com/jtuckerfoltz/LockedPolyominoTilings">GitHub repository with Python code and pictures of all tilings</a>. %H A365862 Wikipedia, <a href="https://en.wikipedia.org/wiki/Pentomino">Pentomino</a>. %e A365862 a(4) = 2: %e A365862 ._______________________________________. %e A365862 |_. | ._. | ._|_. |_________|_________| | %e A365862 | | |_| |_| |_. | ._|_. | ._. | ._| .___| %e A365862 | |___| |___| | |_| ._| |_| |_| | |_|_. | %e A365862 | | |_____| ._| | ._| |___| |___| .___| | %e A365862 | |___. |___| |_|_| |_. |_____| |_| |___| %e A365862 |_| ._|_| |_______| ._|___| | |_. |___. | %e A365862 | | |___. |_. | |___|_______| ._|___| |_| %e A365862 | |___| |_| | |_______| | ._| |_______| | %e A365862 | | .___| ._| |_. | .___| | |_|_. |_. ._| %e A365862 | |_| |___| |_| | |_|_. | |_. ._|_. |_| | %e A365862 |_| |_. |___. | |___| | |_| |_| ._|_| | | %e A365862 | .___|___| |_| | .___|___| | ._| .___| | %e A365862 |_| ._____| |___|_|_____. | |_| |_|_. | | %e A365862 | |_|_. |_. | ._____| ._|_|___| .___| |_| %e A365862 |___. |_. |_|_|_. |_. |___. ._|_| |___| | %e A365862 | ._|_| |_|_. ._|_. |_| | |_| ._|___. | | %e A365862 | |___. | ._| |_. |_| ._| | ._|_. ._|_| | %e A365862 |___| |_| | |_| | |___| | |_| ._| |_. | | %e A365862 | .___|___|_____|___|_. |___| | |_| | |_| %e A365862 |_|_________|_________|___|___|_____|___| (*2) %K A365862 nonn,more %O A365862 0,5 %A A365862 _Jamie Tucker-Foltz_, Sep 29 2023 %E A365862 a(8) from _Jamie Tucker-Foltz_, Oct 30 2023