A033848 Numbers whose prime factors are 2 and 11.

22, 44, 88, 176, 242, 352, 484, 704, 968, 1408, 1936, 2662, 2816, 3872, 5324, 5632, 7744, 10648, 11264, 15488, 21296, 22528, 29282, 30976, 42592, 45056, 58564, 61952, 85184, 90112, 117128, 123904, 170368, 180224, 234256, 247808, 322102

Offset

1,1

Comments

Numbers k such that phi(k)/k = 5/11. - Michel Marcus, Sep 22 2012

Links

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

Formula

A143201(a(n)) = 10. - Reinhard Zumkeller, Sep 13 2011

Sum_{n>=1} 1/a(n) = 1/10. - Amiram Eldar, Dec 22 2020

Maple

N:= 10^6: # to get all terms <= N
S:= {seq(seq(2^i*11^j, i=1..ilog2(floor(N/11^j))), j=1..floor(log[11](N/2)))}:
sort(convert(S, list)); # Robert Israel, Oct 26 2017

Mathematica

Select[Range[10^6], FactorInteger[#][[All, 1]] == {2, 11} &] (* Michael De Vlieger, Oct 26 2017 *)
Sort[Flatten[Table[Table[2^j 11^k, {j, 1, 8}], {k, 1, 8}]]] (* Vincenzo Librandi, Oct 27 2017 *)

Prog

(Haskell)
import Data.Set (singleton, deleteFindMin, insert)
a033848 n = a033848_list !! (n-1)
a033848_list = f (singleton (2*11)) where
   f s = m : f (insert (2*m) $ insert (11*m) s') where
     (m, s') = deleteFindMin s
-- Reinhard Zumkeller, Sep 13 2011

Crossrefs

Cf. A033845, A033846, A033847, A033849, A033850, A033851, A143201.

Sequence in context: A248422 A071266 A038153 * A084024 A342171 A092328

Adjacent sequences: A033845 A033846 A033847 * A033849 A033850 A033851

Keyword

nonn

Author

Jeff Burch

Status

approved