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 A173999 #16 Jun 02 2025 02:43:08
%S A173999 0,1,3,4,5,8,9,10,12,13,14,15,17,24,25,27,29,30,31,37,38,39,40,42,43,
%T A173999 44,45,46,47,48,49,51,55,56,58,61,62,64,66,68,79,80,86,90,91,94,95,96,
%U A173999 99,100,103,109,110,111,115,120,122,123,129,130,131,133,137,138,139,141
%N A173999 Successive positions of odd digits in decimal expansion of Pi (position 0 means 3 before comma or decimal point).
%e A173999 Pi=3,141592653589793...
%e A173999 0 in this sequence because 3 is odd.
%e A173999 1 in this sequence because 1 is odd.
%e A173999 2 is not in this sequence because second digit after comma 4 is not even.
%t A173999 s = First[RealDigits[N[Pi, 1000]]]; aa = {}; Do[If[OddQ[s[[n]]], AppendTo[aa, n - 1]], {n, 1, Length[s]}]; aa (*Artur Jasinski*)
%t A173999 Flatten[Position[RealDigits[\[Pi],10,150][[1]],_?OddQ]-1] (* _Harvey P. Dale_, Apr 19 2011 *)
%Y A173999 Cf. A000796, A174000.
%K A173999 nonn,base
%O A173999 0,3
%A A173999 _Artur Jasinski_, Mar 05 2010
%E A173999 Edited by _Charles R Greathouse IV_, Aug 02 2010
%E A173999 Definition clarified by _Harvey P. Dale_, Apr 01 2019