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 A301297 #9 Apr 02 2018 15:56:37 %S A301297 0,0,1,1,0,1,2,3,4,4,3,2,1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,13,12, %T A301297 11,10,9,8,7,6,5,4,3,2,1,0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17, %U A301297 18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33 %N A301297 Distance from n to nearest Catalan number. %Y A301297 Cf. A000108, A053188, A080732, A296239. %K A301297 nonn %O A301297 1,7 %A A301297 _N. J. A. Sloane_, Mar 24 2018