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A029747 Numbers of the form 2^k times 1, 3 or 5. 30
1, 2, 3, 4, 5, 6, 8, 10, 12, 16, 20, 24, 32, 40, 48, 64, 80, 96, 128, 160, 192, 256, 320, 384, 512, 640, 768, 1024, 1280, 1536, 2048, 2560, 3072, 4096, 5120, 6144, 8192, 10240, 12288, 16384, 20480, 24576, 32768, 40960, 49152, 65536, 81920, 98304, 131072, 163840, 196608 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Fixed points of the Doudna sequence: A005940(a(n)) = A005941(a(n)) = a(n). - Reinhard Zumkeller, Aug 23 2006

Subsequence of A103969. - R. J. Mathar, Mar 06 2010

LINKS

David A. Corneth, Table of n, a(n) for n = 1..9963 (terms <= 10^1000)

Index entries for linear recurrences with constant coefficients, signature (0,0,2).

FORMULA

a(n) = if n < 6 then n else 2*a(n-3). - Reinhard Zumkeller, Aug 23 2006

G.f.: (1+x+x^2)^2/(1-2*x^3). - R. J. Mathar, Mar 06 2010

Sum_{n>=1} 1/a(n) = 46/15. - Amiram Eldar, Oct 15 2020

EXAMPLE

128 = 2^7 * 1 is in the sequence as well as 160 = 2^5 * 5. - David A. Corneth, Sep 18 2020

MATHEMATICA

m = 200000; Select[Union @ Flatten @ Outer[Times, {1, 3, 5}, 2^Range[0, Floor[Log2[m]]]], # < m &] (* Amiram Eldar, Oct 15 2020 *)

PROG

is(n) = n>>valuation(n, 2) <= 5 \\ David A. Corneth, Sep 18 2020

CROSSREFS

Cf. A122132, A000079, A007283, A020714, A130793.

Sequence in context: A015702 A245709 A253789 * A095381 A233205 A158292

Adjacent sequences:  A029744 A029745 A029746 * A029748 A029749 A029750

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane.

EXTENSIONS

Edited by David A. Corneth and Peter Munn, Sep 18 2020

STATUS

approved

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Last modified May 12 23:35 EDT 2021. Contains 343829 sequences. (Running on oeis4.)