login
Positions of 4's in the decimal expansion of Pi.
3

%I #29 May 31 2021 09:03:39

%S 3,20,24,37,58,60,61,71,88,93,105,120,126,127,146,152,158,163,183,184,

%T 189,193,202,203,218,219,224,228,252,255,263,267,272,274,279,294,297,

%U 304,322,340,349,372,377,385,387

%N Positions of 4's in the decimal expansion of Pi.

%H Vincenzo Librandi, <a href="/A053748/b053748.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(n) = A037003(n) + 1. - _Georg Fischer_, May 31 2021

%e Pi starts off 3.141592653589793238462643383279502884197..., with 4s in the hundredths' (10^(-2)s') place, which is the third digit counting the 3 in the ones' place. Then there's another 4 at the 10^(-19)s' place, which is the twentieth digit counting the initial 3. [_Alonso del Arte_, Oct 07 2013]

%t Flatten[Position[RealDigits[Pi, 10, 1000][[1]], 4]] (* _Vincenzo Librandi_, Oct 07 2013 *)

%Y Cf. A000796, A037003.

%K nonn,base

%O 1,1

%A _Simon Plouffe_, Feb 20 2000