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 A145039 #16 Jan 06 2018 23:00:22 %S A145039 3,7,19,31,107,127,607,1279,2203,4423,86243,110503,216091,756839, %T A145039 1257787,20996011,24036583,25964951 %N A145039 Duplicate of A112633. %K A145039 dead %O A145039 1,1