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%I #10 Aug 04 2023 14:10:32
%S 1,20,33,46,59,72,104,117,130,143,175,188,201,214,246,259,272,285,317,
%T 330,343,356,388,401,414,427,459,472,485,498,511,530,543,556,569,582,
%U 614,627,640,653,685,698,711,724,756,769,782,795,827,840,853,866,898
%N Numbers n such that 7 is the first digit of 7^n.
%t Select[Range[1000],IntegerDigits[7^#][[1]]==7&] (* _Harvey P. Dale_, Aug 04 2023 *)
%o (PARI) : for(n=1,1000, if(floor(7^n/10^(floor(n*log(7)/log(10))))==7,print1(n,",")))
%Y Cf. A067485.
%K nonn,base
%O 1,2
%A _Benoit Cloitre_, Feb 22 2002