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 A291807 #18 Sep 11 2017 10:31:29 %S A291807 1,5,67,3000 %N A291807 The number of symmetric polyomino tilings of n X n square. %C A291807 The sequence gives the number of distinct tilings by polyominoes of a square with side n, considering tilings that have at least one symmetry. As for "free" polyominoes, tilings that are reflections or rotations of each other are not considered distinct. %H A291807 John Mason, <a href="/A291807/a291807_1.pdf">Example symmetric tilings</a> %Y A291807 Cf. A268416 (polyominoes that will fit in n-sided square), A291806 (polyomino tilings of square), A291808 (tilings with distinct polyominoes), A291809 (tilings with differently sized polyominoes). %K A291807 nonn,more %O A291807 1,2 %A A291807 _John Mason_, Sep 01 2017