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 A139721 #2 Feb 22 2020 20:57:36 %S A139721 8,5,1,6,0,1,15,2,17,21,4,19,3,7,13,4,27,23,1,18,0,13,0,5,23,3,8,7,0, %T A139721 1,14,12,32,2,8,5,0,2,13,18,0,6,10,9,3,6,15,11,18,3,10,0,2,0,10,6,5,6, %U A139721 15,7,9,6,18,15,12,13,1,21,1,10,19,25,9,9,14,8,15,2,7,14,5,8,4,0,6,5,12,1 %N A139721 Number of digits between successive occurrences of digit 3 in decimal representation of Pi. %Y A139721 Cf. A135088, A000796. %K A139721 nonn,base %O A139721 1,1 %A A139721 Daniel Drijard (daniel.drijard(AT)cern.ch)