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A147576 Numbers with exactly 3 distinct odd prime divisors {3,5,7}.

%I A147576 #19 Dec 22 2020 03:49:26
%S A147576 105,315,525,735,945,1575,2205,2625,2835,3675,4725,5145,6615,7875,
%T A147576 8505,11025,13125,14175,15435,18375,19845,23625,25515,25725,33075,
%U A147576 36015,39375,42525,46305,55125,59535,65625,70875,76545,77175,91875,99225
%N A147576 Numbers with exactly 3 distinct odd prime divisors {3,5,7}.
%C A147576 Numbers k such that phi(k)/k = m
%C A147576 ( Family of sequences for successive n odd primes )
%C A147576 m=2/3 numbers with exactly 1 distinct prime divisor {3} see A000244
%C A147576 m=8/15 numbers with exactly 2 distinct prime divisors {3,5} see A033849
%C A147576 m=16/35 numbers with exactly 3 distinct prime divisors {3,5,7} see A147576
%C A147576 m=32/77 numbers with exactly 4 distinct prime divisors {3,5,7,11} see A147577
%C A147576 m=384/1001 numbers with exactly 5 distinct prime divisors {3,5,7,11,13} see A147578
%C A147576 m=6144/17017 numbers with exactly 6 distinct prime divisors {3,5,7,11,13,17} see A147579
%C A147576 m=3072/323323 numbers with exactly 7 distinct prime divisors {3,5,7,11,13,17,19} see A147580
%C A147576 m=110592/323323 numbers with exactly 8 distinct prime divisors {3,5,7,11,13,17,19,23} see A147581
%H A147576 Amiram Eldar, <a href="/A147576/b147576.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..100 from Harvey P. Dale)
%F A147576 a(n) = 105 * A108347(n). - _Amiram Eldar_, Mar 10 2020
%F A147576 Sum_{n>=1} 1/a(n) = 1/48. - _Amiram Eldar_, Dec 22 2020
%t A147576 a = {}; Do[If[EulerPhi[x]/x == 16/35, AppendTo[a, x]], {x, 1, 100000}]; a
%t A147576 Select[Range[100000],EulerPhi[#]/#==16/35&] (* _Harvey P. Dale_, Dec 01 2013 *)
%Y A147576 Cf. A060735, A108347, A143207, A147571-A147575, A147576-A147580.
%K A147576 nonn
%O A147576 1,1
%A A147576 _Artur Jasinski_, Nov 07 2008