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 A123780 #7 Jul 21 2017 15:38:06 %S A123780 1,4,33,294,2951,30668,328999,3596934,39932206,448517488,5086259884, %T A123780 58135266335 %N A123780 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 4 which is flat, i.e., with all blocks in parallel position. %Y A123780 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123780 nonn,hard %O A123780 1,2 %A A123780 _Søren Eilers_, Oct 29 2006