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A193303

Squarefree numbers multiplied by powers of three.

1, 2, 3, 5, 6, 7, 9, 10, 11, 13, 14, 15, 17, 18, 19, 21, 22, 23, 26, 27, 29, 30, 31, 33, 34, 35, 37, 38, 39, 41, 42, 43, 45, 46, 47, 51, 53, 54, 55, 57, 58, 59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 73, 74, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89, 90, 91, 93

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OFFSET

1,2

COMMENTS

The asymptotic density of this sequence is 27/(4*Pi^2). - Amiram Eldar, Oct 01 2020

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

MATHEMATICA

lim = 102; sf = Select[Range[lim], SquareFreeQ]; lim3 = 3^Range[0, Log[3, lim]]; Select[Union[Flatten[Outer[Times, sf, lim3]]], # <= lim &]

PROG

(PARI) is(n)=issquarefree(n/3^valuation(n, 3)) \\ Charles R Greathouse IV, Jul 31 2011

CROSSREFS