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 A027983 #28 Jun 09 2025 10:32:53 %S A027983 1,5,14,35,81,180,389,825,1726,3575,7349,15020,30561,61965,125294, %T A027983 252795,509161,1024100,2057549,4130225,8284926,16609455,33282989, %U A027983 66669660,133507081,267285605,535010414 %N A027983 Duplicate of A027974. %K A027983 dead %O A027983 0,2