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 A139903 #22 Jul 14 2019 17:15:20 %S A139903 17,113,137,233,257,353,593,617,857,953,977,1097,1193,1217,1433,1553, %T A139903 1697,1913,2153,2273,2297,2393,2417,2633,2657,2753,2777,2897,3137, %U A139903 3257,3593,3617,3833,4073,4217,4337,4457,4673,4793,4817,4937,5153 %N A139903 Duplicate of A139858. %K A139903 dead %O A139903 1,1