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 A123837 #6 Oct 09 2013 14:20:53 %S A123837 1,1,1,4,7,10,13,61,154,256 %N A123837 Number of ways to build a contiguous building with n LEGO blocks of size 3 X 3 on top of a fixed block of the same size so that the building is symmetric after a rotation by 90 degrees. %C A123837 The base block is not counted among the n and must be the only block in the bottom layer of the building %Y A123837 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123837 nonn %O A123837 1,4 %A A123837 _Søren Eilers_, Oct 29 2006