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 A108621 #10 Feb 12 2019 09:14:56 %S A108621 3,1,4,9,2,6,5,8,9,7,9,3,4,6,2,3,3,5,0,1,9,6,9,3,9,9,3,1,5,9,7,4,4,5, %T A108621 2,3,7,0,6,2,0,8,6,8,0,4,8,2,4,2,0,2,1,4,8,6,5,1,2,2,3,7,9,3,4,4,6,9, %U A108621 5,5,2,3,1,3,8,1,2,8,1,1,5,2,8,4 %N A108621 Pi self-erasure. %C A108621 Get Pi's decimal expansion: 3,1,4,1,5,9,2,6,5,3,5,8,9,7,9,3,2,3,8,4,6,2,6,4,3,3,8,3,... ... %C A108621 10 For a=1 to infinity ... %C A108621 20 Let b = the a-th non-erased digit ... %C A108621 30 Jump b digit(s) and erase the digit on which you land ... %C A108621 40 Next a %C A108621 Erased digits are between brackets: 3,1,4,(1),(5),9,2,6,5,(3),(5),8,9,7,9,3,(2),(3),(8),4,6,2,(6),(4),3,(3),(8),3,... %C A108621 Remaining digits build the sequence. %C A108621 [Jumping 0 digit means "erase the closest non-erased digit on your right"] %Y A108621 Cf. A000796. %K A108621 base,easy,nonn %O A108621 1,1 %A A108621 _Eric Angelini_ and _Alexandre Wajnberg_, Jul 06 2005