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 A098891 #53 Nov 19 2023 11:35:40 %S A098891 0,0,1,8,47,266,1339,6544,29837,133495,585002,2542563,10959656 %N A098891 Define the n-omino graph to be the graph whose vertices are each of the n-ominoes, two of which are joined by an edge if one can be obtained from the other by cutting out one of the latter's component squares (thus obtaining an (n-1)-omino for most cases) and gluing it elsewhere. The sequence counts the edges in these graphs. %C A098891 In some cases the act of removing a component square (temporarily) disconnects the polyomino before the component is reattached elsewhere. - _Sean A. Irvine_, Apr 13 2020 %C A098891 See A367435 for the case where the cells remaining after detaching the square to be moved must be a connected polyomino. - _Pontus von Brömssen_, Nov 18 2023 %H A098891 Freddy Barrera, <a href="/A098891/a098891.png">Picture for a(5)</a>, 2020. %H A098891 Freddy Barrera, <a href="/A098891/a098891_1.png">Picture for a(6)</a>, 2020. %H A098891 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a098/A098891.java">Java program</a> (github) %H A098891 FUNG Cheok Yin, <a href="/A098891/a098891.jpg">Tetrominoes</a> %H A098891 FUNG Cheok Yin, <a href="/A098891/a098891_2.txt">Maxima code for n = 4 and n = 5</a>, Apr 13 2020 %Y A098891 Half the row sums of A367126. %Y A098891 Cf. A367435. %K A098891 nonn,more %O A098891 1,4 %A A098891 _Bernardo Recamán_, Nov 08 2004 %E A098891 a(4) corrected by _FUNG Cheok Yin_, Feb 11 2020 %E A098891 a(5) corrected and a(6)-a(12) from _Sean A. Irvine_ and _Freddy Barrera_, Apr 13 2020 %E A098891 a(13) from _Pontus von Brömssen_, Nov 05 2023