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A145784 Numbers with property that the number of prime factors is a multiple of 3. 5
1, 8, 12, 18, 20, 27, 28, 30, 42, 44, 45, 50, 52, 63, 64, 66, 68, 70, 75, 76, 78, 92, 96, 98, 99, 102, 105, 110, 114, 116, 117, 124, 125, 130, 138, 144, 147, 148, 153, 154, 160, 164, 165, 170, 171, 172, 174, 175, 182, 186, 188, 190, 195, 207, 212, 216, 222 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A010872(A001222(a(n))) = 0;

A014612 and A000578 are subsequences.

LINKS

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

MATHEMATICA

Join[{1}, Select[Range[2, 230], Mod[Total[Transpose[FactorInteger[#]][[2]]], 3] == 0 &]] (* T. D. Noe, May 21 2012 *)

PROG

(Haskell)

a145784 n = a145784_list !! (n-1)

a145784_list = filter ((== 0) . a010872 . a001222) [1..]

-- Reinhard Zumkeller, May 26 2012

CROSSREFS

Cf. A028260.

Sequence in context: A051144 A067537 A046339 * A014612 A226527 A212582

Adjacent sequences:  A145781 A145782 A145783 * A145785 A145786 A145787

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Oct 19 2008

STATUS

approved

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Last modified February 22 12:00 EST 2018. Contains 299452 sequences. (Running on oeis4.)