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%I #10 Feb 22 2018 19:06:16
%S 0,4,3,2,8,14,1,7,13,45,6,38,12,57,31,5,50,37,11,69,43,30,17,4,49,36,
%T 23,10,68,55,42,29,16,3,61,48,35,106,22,9,67,138,54,41,28,99,15,228,2,
%U 60,131,47,260,34,21,92,8,150,66,137,53,195,40,182,27,98,14,85,298,72,285
%N 7^a(n) is smallest power of 7 beginning with n.
%H D. Mondot, <a href="/A018866/b018866.txt">Table of n, a(n) for n=1..32699</a>
%t With[{s=7^Range[0,500]},Flatten[Table[Position[s,_?(IntegerDigits[n] == Take[IntegerDigits[#],IntegerLength[n]]&),1,1],{n,80}]]]-1//Quiet (* _Harvey P. Dale_, Feb 22 2018 *)
%K nonn,base
%O 1,2
%A _David W. Wilson_
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