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 A053747 #23 May 31 2021 09:11:37 %S A053747 1,10,16,18,25,26,28,44,47,65,87,92,112,116,124,138,143,171,195,197, %T A053747 216,217,231,232,238,262,266,275,283,284,286,301,314,347,350,359,365, %U A053747 366,369,383,402,403,410,421,431 %N A053747 Positions of 3's in the decimal expansion of Pi. %H A053747 Vincenzo Librandi, <a href="/A053747/b053747.txt">Table of n, a(n) for n = 1..1000</a> %H A053747 <a href="/index/Ph#Pi314">Index entries for sequences related to the number Pi</a> %F A053747 a(1) = 1, a(n) = A037002(n-1) + 1 for n >= 2. - _Georg Fischer_, May 31 2021 %t A053747 Flatten[Position[RealDigits[Pi, 10, 1000][[1]], 3]] (* _Vincenzo Librandi_, Oct 07 2013 *) %Y A053747 Cf. A037002. %K A053747 nonn,base %O A053747 1,2 %A A053747 _Simon Plouffe_, Feb 20 2000