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 A210435 #40 Oct 19 2024 15:57:32
%S A210435 1,1,2,3,3,4,5,5,6,7,7,8,9,10,10,11,12,12,13,14,14,15,16,17,17,18,19,
%T A210435 19,20,21,21,22,23,24,24,25,26,26,27,28,28,29,30,31,31,32,33,33,34,35,
%U A210435 35,36,37,38,38,39,40,40,41,42,42,43,44,45,45,46,47,47
%N A210435 Number of digits in 5^n.
%H A210435 Seiichi Manyama, <a href="/A210435/b210435.txt">Table of n, a(n) for n = 0..10000</a>
%H A210435 Ana Rechtman, <a href="http://images-archive.math.cnrs.fr/Octobre-2015-3e-defi.html">Octobre 2015, 3e Défi</a>, Images des Mathématiques, CNRS, 2015 (in French).
%F A210435 a(n) = A055642(A000351(n)) = A055642(5^n) = floor(log_10(10*(5^n))). [_Jonathan Vos Post_, Mar 22 2012]
%F A210435 a(n) + A034887(n) = n+1. - _Michel Marcus_, Oct 27 2015
%e A210435 a(4) = 3 because 5^4 = 625, which has 3 digits.
%e A210435 a(5) = 4 because 5^5 = 3125, which has 4 digits.
%p A210435 a:= n-> length(5^n): seq(a(n), n=0..100); # _Alois P. Heinz_, Mar 22 2012
%t A210435 Table[Length[IntegerDigits[5^n]], {n, 0, 67}] (* _Bruno Berselli_, Mar 22 2012 *)
%t A210435 IntegerLength[5^Range[0,70]] (* _Harvey P. Dale_, Mar 26 2013 *)
%o A210435 (Magma) [#Intseq(5^n): n in [0..67]]; // _Bruno Berselli_, Mar 22 2012
%o A210435 (PARI) a(n) = #Str(5^n); \\ _Michel Marcus_, Oct 27 2015
%Y A210435 Cf. A000351, A055642.
%Y A210435 Number of digits in b^n: A034887 (b=2), A034888 (b=3), A210434 (b=4), A210435 (b=5), A210436 (b=6), A210062 (b=7).
%K A210435 nonn,base,easy
%O A210435 0,3
%A A210435 _Luc Comeau-Montasse_, Mar 21 2012