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 A123771 #14 Oct 08 2017 05:16:00 %S A123771 1,2,12,45,264,1128,6991,32202,202856,973242,6204349 %N A123771 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 3 which is symmetric after a rotation by 180 degrees. %H A123771 S. Eilers, <a href="http://www.jstor.org/stable/10.4169/amer.math.monthly.123.5.415">The LEGO counting problem</a>, Amer. Math. Monthly, 123 (May 2016), 415-426. %H A123771 <a href="/wiki/Index_to_OEIS:_Section_Lc#LEGO">Index entry for sequences related to LEGO blocks</a> %Y A123771 Cf. A112389, A123762-A123827, A123829-A123849. %K A123771 nonn,more %O A123771 1,2 %A A123771 _Søren Eilers_, Oct 29 2006