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%I #13 Jun 26 2018 19:24:07
%S 1,7,26,43,38,57,48,64,81,92,91,78,104,151,155,143,162,150,173,249,
%T 267,251,339,282,333,325,275,378,345,428,415,429,473,463,411,430,513,
%U 420,507,546,508,489,533,603,566,593,641,545,707,638,722
%N Smallest k such that 4^k has exactly n 3's in its decimal representation.
%H Robert Israel, <a href="/A063578/b063578.txt">Table of n, a(n) for n = 0..1000</a>
%p N:= 100: # to get a(0) to a(N)
%p A:= Array(0..N):
%p count:= 0:
%p for n from 1 while count < N+1 do
%p v:= numboccur(3, convert(4^n,base,10));
%p if v <= N and A[v] = 0 then
%p count:= count+1;
%p A[v]:= n;
%p fi
%p od:
%p seq(A[i],i=0..N); # _Robert Israel_, Feb 24 2016
%t a = {}; Do[k = 1; While[ Count[ IntegerDigits[4^k], 3] != n, k++ ]; a = Append[a, k], {n, 0, 50} ]; a
%Y Cf. A063576, A063577, A063579, A063580, A063581, A063582, A063583, A063584.
%K base,nonn
%O 0,2
%A _Robert G. Wilson v_, Aug 10 2001
%E Name corrected by _Jon E. Schoenfield_, Jun 26 2018
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