A242594 - OEIS

%I #17 Oct 23 2018 07:08:37

%S 1,6,11,16,21,26,31,36,41,46,99,104,109,114,119,124,129,134,139,144,

%T 197,202,207,212,217,222,227,232,237,242,295,300,305,310,315,320,325,

%U 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 Numbers k such that 4^k has initial digit 4.

%H Robert Israel, <a href="/A242594/b242594.txt">Table of n, a(n) for n = 1..9693</a>

%F a(n) = log_4(A067482(n)).

%e 6 is in the sequence because 4^6 = 4096 starts with 4.

%p 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 Cf. A067482.

%K nonn,base

%O 1,2

%A _Robert Israel_, May 18 2014