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A072587 Numbers having at least one prime factor with an even exponent. 11
4, 9, 12, 16, 18, 20, 25, 28, 36, 44, 45, 48, 49, 50, 52, 60, 63, 64, 68, 72, 75, 76, 80, 81, 84, 90, 92, 98, 99, 100, 108, 112, 116, 117, 121, 124, 126, 132, 140, 144, 147, 148, 150, 153, 156, 162, 164, 169, 171, 172, 175, 176, 180, 188, 192, 196, 198, 200, 204 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of the union of {1} and A002035. [Correction, Nov 15 2012]

A162645 is a subsequence and this sequence is a subsequence of A162643. - Reinhard Zumkeller, Jul 08 2009

Numbers whose sum of divisors is greater than the sum of bi-unitary divisors: A000203(a(n)) > A188999(a(n)). - Paolo P. Lava, Oct 08 2014

LINKS

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

MATHEMATICA

Select[Range[210], MemberQ[EvenQ[Transpose[FactorInteger[#]][[2]]], True] &] (* Harvey P. Dale, Apr 03 2012 *)

PROG

(Haskell)

a072587 n = a072587_list !! (n-1)

a072587_list = tail $ filter (any even . a124010_row) [1..]

-- Reinhard Zumkeller, Nov 15 2012

(PARI) is(n)=n>3 && Set(factor(n)[, 2]%2)[1]==0 \\ Charles R Greathouse IV, Oct 16 2015

CROSSREFS

Cf. A000037, A072588, A124010.

Sequence in context: A066423 A072498 A162643 * A240112 A162645 A135572

Adjacent sequences:  A072584 A072585 A072586 * A072588 A072589 A072590

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 23 2002

EXTENSIONS

Thanks to Zak Seidov who noticed that 1 had to be removed. - Reinhard Zumkeller, Nov 15 2012

STATUS

approved

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Last modified January 23 22:36 EST 2020. Contains 331177 sequences. (Running on oeis4.)