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 A367294 #9 Nov 12 2023 21:56:19 %S A367294 2,12,22,32,42,52,62,72,82,92,105,115,125,135,145,155,165,175,185,198, %T A367294 208,218,228,238,248,258,268,278,288,301,311,321,331,341,351,361,371, %U A367294 381,394,404,414,424,434,444,454,464,474,484,497,507,517,527,537,547 %N A367294 Numbers k such that 4 is the first digit of 2^k. %C A367294 The asymptotic density of this sequence is log_10(5/4) = 0.096910... %p A367294 x := 1: %p A367294 L := []: %p A367294 for n from 0 to 10^3 do %p A367294 if 4 <= x and x < 5 then %p A367294 L := [op(L), n] %p A367294 fi; %p A367294 x := 2*x; %p A367294 if x > 10 then %p A367294 x := (1/10)*x fi; %p A367294 od: %p A367294 L; %t A367294 Select[Range[550], IntegerDigits[2^#][[1]] == 4 &] (* _Amiram Eldar_, Nov 12 2023 *) %Y A367294 Cf. A000079, A067497, A067469, A172404, A363060, A367295, A330243, A367296, A097415. %K A367294 nonn,base %O A367294 1,1 %A A367294 _Martin Renner_, Nov 12 2023