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 A123787 #7 Feb 15 2025 15:27:24 %S A123787 1,2,28,192,1680,13644,118916,1044873,9160772 %N A123787 Number of ways, counted up to symmetry, to build a contiguous building with n LEGO blocks of size 1 X 5 which is symmetric after a rotation by 180 degrees. %Y A123787 Cf. A112389, A123762 - A123827, A123829 - A123849. %K A123787 nonn %O A123787 1,2 %A A123787 _Søren Eilers_, Oct 29 2006