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 A123825 #7 Feb 15 2025 15:34:43 %S A123825 1,1,25,53,1189,2947,66094,181955,3979943 %N A123825 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 2 X 3 which is symmetric after a rotation by 180 degrees. %Y A123825 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123825 nonn %O A123825 1,3 %A A123825 _Søren Eilers_, Oct 29 2006