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 A033186 #19 Jul 07 2020 06:42:43 %S A033186 1,9,6,9,8,4,6,6,4,8,9,0,8,8,4,1,6,9,9,9,1,0,8,0,9,4,9,4,4,9,0,8,1,6, %T A033186 4,0,6,8,6,0,9,8,6,8,0,4,8,4,0,6,9,8,1,4,8,0,8,6,1,8,0,6,6,4,0,9,0,8, %U A033186 1,9,4,0,8,1,8,4,8,1,4,0,8,0,0,8,0,9,6 %N A033186 Remove all 2's from decimal expansion of Pi, then all 3's, ..., then all 11's, ... (running through primes in order) with the restriction that only digits contiguous in the original expansion are removed. %C A033186 The condition to remove only contiguous digits in the original expansion ensures this sequence is well-defined. If the sequence were to be "closed up" after each prime removed, then any given initial portion will (almost certainly) be the prefix of some prime larger than those removed so far. - _Sean A. Irvine_, Jul 06 2020 %C A033186 The sequence of primes removed is given by A033274. - _Sean A. Irvine_, Jul 05 2020 %H A033186 Sean A. Irvine, <a href="/A033186/b033186.txt">Table of n, a(n) for n = 1..8200</a> %H A033186 Sean A. Irvine, <a href="https://github.com/archmageirvine/joeis/blob/master/src/irvine/oeis/a033/A033186.java">Java program</a> (github) %e A033186 From _Sean A. Irvine_, Jul 05 2020: (Start) %e A033186 Using "z" to denote deleted portions: %e A033186 31415926535897932... %e A033186 314159z653589793z... (replace 2) %e A033186 z14159z65z58979zz... (replace 3) %e A033186 z141z9z6zzz8979zz... (replace 5) %e A033186 z141z9z6zzz89z9zz... (replace 7) %e A033186 ... %e A033186 z1zz9z6zzz89z9zz... (replace 41) %e A033186 ... %e A033186 z1zz9z6zzzzz9zz... (replace 89) %e A033186 Hence sequence starts, 1, 9, 6, 9, ... %e A033186 (End) %K A033186 nonn,base %O A033186 1,2 %A A033186 _Simon Plouffe_ %E A033186 Definition and data modified by _Simon Plouffe_ and _Sean A. Irvine_, Jul 05 2020