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%I #7 Jan 17 2015 13:56:35
%S 4,5,7,10,14,14,16,17,42,24,47,25,29,39,31,40,41,45,40,69,46,65,807,
%T 128,67,89,55,217,87,76,74,72,99,70,75,144,78,213,96,233,114,103,457,
%U 108,156,163,140,97,127,270,109,127,167,135,128,131,196,133,309,138,148,140,813,169,135,148,235,7235
%N a(n) is number of digits of the smallest term of the sequence A248857 which is of the form 4^n*(5^(2n-1)*10^m-1).
%e a(1) = number of digits of 1996 = 4.
%e a(2) = number of digits of 19984 = 5.
%e a(3) = number of digits of 1999936 = 7 and
%e a(68)=7235, because smallest prime of the form 5^(2*68-1)*10^m -1 is 5^135*10^7099-1 and 4^68(5^135*10^7099-1) has 7235 digits.
%Y Cf. A248857.
%K nonn,base
%O 1,1
%A _Farideh Firoozbakht_, Jan 06 2015
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