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 A054565 #20 Dec 11 2020 19:23:31 %S A054565 1,18,20,22,41,43,62,64,66,83,85,87,106,108,110,127,129,131,150,152, %T A054565 171,173,175,194,196,215,217,219,236,238,240,259,261,263,280,282,284, %U A054565 303,305,324,326,328,347,349,368,370,372,389,391,393,412,414,416,433 %N A054565 Numbers n such that 3 is the first digit of 3^n. %H A054565 Vincenzo Librandi, <a href="/A054565/b054565.txt">Table of n, a(n) for n = 1..1000</a> %t A054565 Select[Range[500],First[IntegerDigits[3^#]]==3&] (* _Harvey P. Dale_, Dec 23 2012 *) %o A054565 (PARI) for(n=1,100, if(floor(3^n/10^(floor(n*log(3)/log(10))))==3,print1(n,","))) %Y A054565 Cf. A067481. %K A054565 nonn,base %O A054565 1,2 %A A054565 _Benoit Cloitre_, Feb 22 2002 %E A054565 Corrected by _T. D. Noe_, Nov 01 2006 %E A054565 Corrected by _Harvey P. Dale_, Dec 23 2012