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 A291303 #3 Aug 31 2017 23:36:35 %S A291303 1,2,4,2,5,4,5 %N A291303 Appears to be an erroneous version of A019294. %C A291303 Included in accordance with OEIS policy of including published but incorrect versions of sequences. %D A291303 Richard K. Guy, Unsolved Problems in Number Theory, 3rd Edition, Springer, 2004. See Section B41, p. 147. %K A291303 dead %O A291303 1,2