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 A123817 #14 Sep 16 2018 09:56:20 %S A123817 1,5,9,51,131,807,2129,13967,39701,265152,781478,5287858,16094282, %T A123817 110147280,342365511,2360643691 %N A123817 Number of ways to build a contiguous building with n LEGO blocks of size 1 X 8 on top of a fixed block of the same size so that the building is flat, i.e., with all blocks in parallel position and symmetric after a rotation by 180 degrees. %C A123817 The base block is not counted among the n and must be the only block in the bottom layer of the building. %H A123817 <a href="/wiki/Index_to_OEIS:_Section_Lc#LEGO">Index entry for sequences related to LEGO blocks</a> %Y A123817 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123817 nonn %O A123817 1,2 %A A123817 _Søren Eilers_, Oct 29 2006 %E A123817 a(11)-a(16) from _Søren Eilers_, Sep 16 2018