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 A175852 #5 Dec 10 2016 18:49:38
%S A175852 5,25,625,3125,78125,390625,9765625,48828125,244140625,6103515625,
%T A175852 30517578125,762939453125,3814697265625,95367431640625,
%U A175852 476837158203125,2384185791015625,59604644775390625,298023223876953125
%N A175852 a(n) = the highest power of 5 with n decimal digits.
%C A175852 a(n) = 5^d(n), with
%C A175852 d(n) = {1, 2, 4, 5, 7, 8, 10, 11, 12, 14, 15, 17, 18, 20, 21, 22, 24, 25, 27, 28}.
%C A175852 If we redefine the sequence as a(n) = the highest power of 5 less than 10^n, then keyword "base" may be omitted.
%C A175852 d(n) = A066344(n). - _Zak Seidov_, Oct 01 2010
%t A175852 d[n_]=Floor@Log[5, 10^n]; a[n_]=5^d[n]
%K A175852 base,nonn
%O A175852 1,1
%A A175852 _Zak Seidov_, Sep 29 2010