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A003593
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Numbers of the form 3^i*5^j with i, j >= 0.
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22
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1, 3, 5, 9, 15, 25, 27, 45, 75, 81, 125, 135, 225, 243, 375, 405, 625, 675, 729, 1125, 1215, 1875, 2025, 2187, 3125, 3375, 3645, 5625, 6075, 6561, 9375, 10125, 10935, 15625, 16875, 18225, 19683, 28125, 30375, 32805, 46875, 50625, 54675, 59049
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graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,2
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COMMENTS
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Odd 5-smooth numbers (A051037). - Reinhard Zumkeller, Sep 18 2005
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LINKS
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_Reinhard Zumkeller_, Table of n, a(n) for n = 1..10000
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FORMULA
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a(n) =1/sqrt(15)*exp(sqrt(2*ln(3)*ln(5)*n)) asymptotically - Benoit Cloitre, Jan 22 2002
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MATHEMATICA
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fQ[n_] := PowerMod[15, n, n] == 0; Select[Range[60000], fQ] (* Bruno Berselli, Sep 24 2012 *)
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PROG
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(PARI) list(lim)=my(v=List(), N); for(n=0, log(lim)\log(5), N=5^n; while(N<=lim, listput(v, N); N*=3)); vecsort(Vec(v)) \\ Charles R Greathouse IV, Jun 28 2011
(PARI) is(n)=n==3^valuation(n, 3)*5^valuation(n, 5) \\ Charles R Greathouse IV, Apr 23 2013
(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a003593 n = a003593_list !! (n-1)
a003593_list = f (singleton 1) where
f s = m : f (insert (3*m) $ insert (5*m) s') where
(m, s') = deleteFindMin s
-- Reinhard Zumkeller, Sep 13 2011
(MAGMA) [n: n in [1..60000] | PrimeDivisors(n) subset [3, 5]]; // Bruno Berselli, Sep 24 2012
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CROSSREFS
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Cf. A033849, A112751-A112756, A143202.
Sequence in context: A057235 A057289 A056754 * A120027 A018586 A135342
Adjacent sequences: A003590 A003591 A003592 * A003594 A003595 A003596
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KEYWORD
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nonn,changed
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AUTHOR
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N. J. A. Sloane.
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STATUS
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approved
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