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%I #12 Aug 12 2019 02:23:04
%S 0,0,1,0,1,2,0,1,2,0,3,1,2,0,3,1,4,2,0,3,1,4,2,0,5,3,1,4,2,0,5,3,1,6,
%T 4,2,0,5,3,1,6,4,2,7,0,5,3,1,6,4,2,7,0,5,3,8,1,6,4,2,7,0,5,3,8,1,6,4,
%U 9,2,7,0,5,3,8,1,6,4,9,2,7,0,5,10,3,8,1,6,4,9,2,7,0,5,10,3,8,1,6,11,4,9,2,7,0,5
%N Exponent of 7 (value of j) in n-th number of form 4^i*7^j.
%H Robert Israel, <a href="/A025666/b025666.txt">Table of n, a(n) for n = 1..10000</a>
%F 4^A025648(n)*7^a(n) = A025619(n). - _Robert Israel_, Aug 11 2019
%p N:= 10^10: # to consider all terms with 4^i*7^j<=N
%p S:= {seq(seq(4^i*7^j, j=0..floor(log[7](N/4^i))),i=0..floor(log[4](N)))}:
%p map(padic:-ordp, sort(convert(S,list)),7); # _Robert Israel_, Aug 11 2019
%Y Cf. A025619, A025648.
%K nonn
%O 1,6
%A _David W. Wilson_
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