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Positions of 3's in the decimal expansion of Pi.
3

%I #23 May 31 2021 09:11:37

%S 1,10,16,18,25,26,28,44,47,65,87,92,112,116,124,138,143,171,195,197,

%T 216,217,231,232,238,262,266,275,283,284,286,301,314,347,350,359,365,

%U 366,369,383,402,403,410,421,431

%N Positions of 3's in the decimal expansion of Pi.

%H Vincenzo Librandi, <a href="/A053747/b053747.txt">Table of n, a(n) for n = 1..1000</a>

%H <a href="/index/Ph#Pi314">Index entries for sequences related to the number Pi</a>

%F a(1) = 1, a(n) = A037002(n-1) + 1 for n >= 2. - _Georg Fischer_, May 31 2021

%t Flatten[Position[RealDigits[Pi, 10, 1000][[1]], 3]] (* _Vincenzo Librandi_, Oct 07 2013 *)

%Y Cf. A037002.

%K nonn,base

%O 1,2

%A _Simon Plouffe_, Feb 20 2000