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 A354380 #7 May 25 2022 11:48:07 %S A354380 1,10,91,1432,23547,416177,7544247,139666895,2623895224 %N A354380 Number of free pseudo-polytans with n cells. %C A354380 A pseudo-polytan is a planar figure consisting of n isosceles right triangles joined either edge-to-edge or corner-to-corner, in such a way that the short edges of the triangles coincide with edges of the square lattice. Two figures are considered equivalent if they differ only by a rotation or reflection. %C A354380 The pseudo-polytans are constructed in the same way as ordinary polytans (A006074), but allowing for corner-connections. Thus they generalize polytans in the same way that pseudo-polyominoes (aka polyplets, A030222) generalize ordinary polyominoes (A000105). %H A354380 Aaron N. Siegel, <a href="/A354380/a354380.png">Illustration showing a(2) = 10</a>. The color of each figure corresponds to its number of symmetries. %e A354380 a(2) = 10, because there are 10 ways of adjoining two isosceles right triangles: 3 distinct edge-to-edge joins (cf. A006074), and 7 distinct corner-to-corner joins. %Y A354380 Cf. A006074, A000105, A030222. %K A354380 nonn,hard,more %O A354380 1,2 %A A354380 _Aaron N. Siegel_, May 24 2022