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 A213378 #8 Jun 26 2022 03:27:59 %S A213378 0,1,3,41,499,6946,95964,1330807,18395673 %N A213378 Number of polyominoes of order 2n that can be tiled by dominoes in more than one way. %C A213378 Tilings related by a symmetry of the polyomino that is not a symmetry of the tiling count as distinct (thus, the square tetromino counts as being tiled in two distinct ways). %Y A213378 Cf. A056785, A056786, A213376, A213377. %K A213378 hard,more,nonn %O A213378 1,3 %A A213378 _Joseph Myers_, Jun 10 2012