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A033851 Numbers n whose prime factors are 5 and 7. 13
35, 175, 245, 875, 1225, 1715, 4375, 6125, 8575, 12005, 21875, 30625, 42875, 60025, 84035, 109375, 153125, 214375, 300125, 420175, 546875, 588245, 765625, 1071875, 1500625, 2100875, 2734375, 2941225, 3828125, 4117715, 5359375, 7503125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

From Artur Jasinski, Nov 09 2008: (Start)

Successive k such that EulerPhi[k]/k == 24/35.

a(n)=35*A003595(n) (End)

A143201(a(n)) = 3; subsequence of A143202. [Reinhard Zumkeller, Sep 13 2011]

LINKS

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

MATHEMATICA

a = {}; Do[If[EulerPhi[x]/x == 24/35, AppendTo[a, x]], {x, 1, 10000}]; a (* Artur Jasinski, Nov 09 2008 *)

Take[With[{nn=10}, Sort[Flatten[Table[5^i 7^j, {i, nn}, {j, nn}]]]], 40] (* Harvey P. Dale, Feb 09 2013 *)

PROG

(Haskell)

import Data.Set (singleton, deleteFindMin, insert)

a033851 n = a033851_list !! (n-1)

a033851_list = f (singleton (5*7)) where

   f s = m : f (insert (5*m) $ insert (7*m) s') where

     (m, s') = deleteFindMin s

-- Reinhard Zumkeller, Sep 13 2011

CROSSREFS

Cf. A003595, A147571-A147575, A147576-A147580 [From Artur Jasinski, Nov 09 2008]

Cf. A033845, A033846, A033847, A033848, A033849, A033850.

Subsequence of A256617.

Sequence in context: A228453 A327651 A319042 * A219825 A194716 A220047

Adjacent sequences:  A033848 A033849 A033850 * A033852 A033853 A033854

KEYWORD

nonn

AUTHOR

Jeff Burch

EXTENSIONS

Offset fixed by Reinhard Zumkeller, Sep 13 2011

STATUS

approved

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Last modified December 3 20:35 EST 2020. Contains 338920 sequences. (Running on oeis4.)