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 A123819 #6 Oct 09 2013 14:20:53 %S A123819 1,1,5,8,65,126,1023,2187,17585,39606,315326,737302 %N A123819 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 2 which is symmetric after a rotation by 180 degrees. %Y A123819 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123819 nonn %O A123819 1,3 %A A123819 _Søren Eilers_, Oct 29 2006