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%I #32 Oct 19 2022 15:31:46
%S 15,45,75,135,225,375,405,675,1125,1215,1875,2025,3375,3645,5625,6075,
%T 9375,10125,10935,16875,18225,28125,30375,32805,46875,50625,54675,
%U 84375,91125,98415,140625,151875,164025,234375,253125,273375,295245
%N Numbers whose prime factors are 3 and 5.
%C Numbers k such that phi(k) = (8/15)*k. - _Benoit Cloitre_, Apr 19 2002
%C Subsequence of A143202. - _Reinhard Zumkeller_, Sep 13 2011
%H Reinhard Zumkeller, <a href="/A033849/b033849.txt">Table of n, a(n) for n = 1..10000</a>
%F From _Reinhard Zumkeller_, Sep 13 2011: (Start)
%F A143201(a(n)) = 3.
%F a(n) = 15*A003593(n). (End)
%F Sum_{n>=1} 1/a(n) = 1/8. - _Amiram Eldar_, Dec 22 2020
%t Sort[Flatten[Table[Table[3^j*5^k, {j, 1, 10}], {k, 1, 10}]]] (* _Geoffrey Critzer_, Dec 07 2014 *)
%t Select[Range[300000],FactorInteger[#][[All,1]]=={3,5}&] (* _Harvey P. Dale_, Oct 19 2022 *)
%o (Haskell)
%o import Data.Set (singleton, deleteFindMin, insert)
%o a033849 n = a033849_list !! (n-1)
%o a033849_list = f (singleton (3*5)) where
%o f s = m : f (insert (3*m) $ insert (5*m) s') where
%o (m,s') = deleteFindMin s
%o -- _Reinhard Zumkeller_, Sep 13 2011
%Y Cf. A033845, A033846, A033847, A033848, A033850, A033851, A143201, A143202.
%Y Subsequence of A256617.
%K nonn
%O 1,1
%A _Jeff Burch_
%E Offset and typo in data fixed by _Reinhard Zumkeller_, Sep 13 2011
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