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A033849 Numbers n whose prime factors are 3 and 5. 20
15, 45, 75, 135, 225, 375, 405, 675, 1125, 1215, 1875, 2025, 3375, 3645, 5625, 6075, 9375, 10125, 10935, 16875, 18225, 28125, 30375, 32805, 46875, 50625, 54675, 84375, 91125, 98415, 140625, 151875, 164025, 234375, 253125, 273375, 295245 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

n such that phi(n)=(8/15)*n. - Benoit Cloitre, Apr 19 2002

A143201(a(n))=3; subsequence of A143202; a(n)=15*A003593(n). - Reinhard Zumkeller, Sep 13 2011

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

MATHEMATICA

Sort[Flatten[Table[Table[3^j*5^k, {j, 1, 10}], {k, 1, 10}]]] (* Geoffrey Critzer, Dec 07 2014 *)

PROG

(Haskell)

import Data.Set (singleton, deleteFindMin, insert)

a033849 n = a033849_list !! (n-1)

a033849_list = f (singleton (3*5)) where

   f s = m : f (insert (3*m) $ insert (5*m) s') where

     (m, s') = deleteFindMin s

-- Reinhard Zumkeller, Sep 13 2011

CROSSREFS

Cf. A033845, A033846, A033847, A033848, A033850, A033851.

Subsequence of A256617.

Sequence in context: A298462 A066763 A164788 * A194715 A060536 A014634

Adjacent sequences:  A033846 A033847 A033848 * A033850 A033851 A033852

KEYWORD

nonn

AUTHOR

Jeff Burch

EXTENSIONS

Offset and typo in data fixed by Reinhard Zumkeller, Sep 13 2011

STATUS

approved

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Last modified December 13 01:23 EST 2019. Contains 329963 sequences. (Running on oeis4.)