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%I #16 May 14 2014 18:21:26
%S 1,3,7,9,10,11,13,17,19,21,23,27,29,30,31,33,37,39,41,43,47,49,51,53,
%T 57,59,61,63,67,69,70,71,73,77,79,81,83,87,89,90,91,93,97,99,100,101,
%U 103,107,109,110,111,113,117,119,121,123,127,129,130,131,133
%N Numbers of the form m * 10^k where gcd(10, m) = 1 and k >= 0 and m > 0.
%C Also natural numbers x such that fractions of the form x/10^r, after reduction to lowest terms, still have a power of ten in the denominator.
%C Superset of A045572, and every member of a(n) arises from a member of A045572 by appending zero or more '0' digits at the right.
%F a(n) = 9n/4 + O(log n). - _Charles R Greathouse IV_, May 14 2014
%e 19/10 is already fully reduced, and has a power of 10 in its denominator, so 19 is in the sequence;
%e 30/100 reduces to 3/10, which has a power of 10 in its denominator, so 30 is in the sequence;
%e 12/10, 15/100, and 20/100 reduce to 6/5, 3/20, and 1/5, respectively (none of which has a power of 10 in its denominator), so 12, 15, and 20 are not in the sequence.
%o (PARI) for(i=1,400,if(valuation(i,2)==valuation(i,5),print1(i,", ")))
%o (PARI) is(n)=gcd(n/10^valuation(n,10),10)==1 \\ _Charles R Greathouse IV_, May 14 2014
%Y Cf. A064615 (uses 6 instead of 10).
%K nonn,easy
%O 1,2
%A _Jeppe Stig Nielsen_, Apr 26 2014
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