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 A242594 #17 Oct 23 2018 07:08:37 %S A242594 1,6,11,16,21,26,31,36,41,46,99,104,109,114,119,124,129,134,139,144, %T A242594 197,202,207,212,217,222,227,232,237,242,295,300,305,310,315,320,325, %U A242594 330,335,393,398,403,408,413,418,423,428,433,491,496,501,506,511,516,521,526,531,584,589,594,599,604,609,614,619 %N A242594 Numbers k such that 4^k has initial digit 4. %H A242594 Robert Israel, <a href="/A242594/b242594.txt">Table of n, a(n) for n = 1..9693</a> %F A242594 a(n) = log_4(A067482(n)). %e A242594 6 is in the sequence because 4^6 = 4096 starts with 4. %p A242594 select(t -> 4^t >= 4*10^ilog10(4^t) and 4^t < 5*10^ilog10(4^t), [$1..1000]); # _Robert Israel_, May 18 2014 %Y A242594 Cf. A067482. %K A242594 nonn,base %O A242594 1,2 %A A242594 _Robert Israel_, May 18 2014