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A171241 Numbers n such that (number of prime divisors of n <= 3) = 3. 1
8, 12, 18, 27, 40, 56, 60, 84, 88, 90, 104, 126, 132, 135, 136, 152, 156, 184, 189, 198, 200, 204, 228, 232, 234, 248, 276, 280, 296, 297, 300, 306, 328, 342, 344, 348, 351, 372, 376, 392, 414, 420, 424, 440, 444, 450, 459, 472, 488, 492, 513, 516, 520, 522 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Numbers of the form k*m where k is in {8, 12, 18, 27} and gcd(m, 6) = 1. - David A. Corneth, Aug 31 2019

LINKS

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

FORMULA

A169611(a(n)) = 3.

MATHEMATICA

aQ[n_] := Plus @@ Last /@ Select[FactorInteger@n, 1 < #[[1]] < 4 &] == 3; Select[Range[522], aQ] (* Amiram Eldar, Aug 31 2019 after Robert G. Wilson v at A169611 *)

PROG

(PARI) is(n) = bigomega(gcd(n, 1296)) == 3 \\ David A. Corneth, Aug 31 2019

CROSSREFS

Cf. A007310, A169611, A171126.

Sequence in context: A028393 A066681 A276403 * A120137 A274951 A033477

Adjacent sequences:  A171238 A171239 A171240 * A171242 A171243 A171244

KEYWORD

nonn,easy

AUTHOR

Juri-Stepan Gerasimov, Dec 05 2009

EXTENSIONS

Corrected (200, 232, 280 inserted) and extended by R. J. Mathar, Jun 04 2010

Name corrected by Amiram Eldar, Aug 31 2019

STATUS

approved

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Last modified October 24 18:08 EDT 2021. Contains 348233 sequences. (Running on oeis4.)