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 A099345 #6 Sep 20 2023 07:47:21
%S A099345 0,7,56,609,6193,62621,624618,6250491,62500734,625010592,6250006866,
%T A099345 62500188610
%N A099345 Frequency of the hexadecimal C in the first 10^n hexadecimal digits of Pi.
%H A099345 Kanada Laboratory, <a href="https://web.archive.org/web/20120324194210/http://pi2.cc.u-tokyo.ac.jp/pi-hexa_current.html">Statistical Distribution Information</a>.
%t A099345 $MaxPrecision = 1100000; ph = Drop[ RealDigits[Pi, 16, 5*10^5] [[1]], 1]; Table[ Count[ Take[ph, 10^n], 12], {n, 5}]
%Y A099345 Cf. A000796, A062964, A099333, A099334, A099335, A099336, A099337, A099338, A099339, A099340, A099341, A099342, A099343, A099344, A099346, A099347, A099348.
%K A099345 base,nonn,more
%O A099345 1,2
%A A099345 _Robert G. Wilson v_, Oct 12 2004