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A162643 Numbers such that their number of divisors is not a power of 2. 7
4, 9, 12, 16, 18, 20, 25, 28, 32, 36, 44, 45, 48, 49, 50, 52, 60, 63, 64, 68, 72, 75, 76, 80, 81, 84, 90, 92, 96, 98, 99, 100, 108, 112, 116, 117, 121, 124, 126, 132, 140, 144, 147, 148, 150, 153, 156, 160, 162, 164, 169, 171, 172, 175, 176, 180, 188, 192, 196, 198 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of A036537;

A072587 is a subsequence.

A number m is a term if and only if it has at least one non-infinitary divisor, or A000005(m) > A037445(m). - Vladimir Shevelev, Feb 23 2017

LINKS

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

FORMULA

A209229(A000005(a(n))) = 0. - Reinhard Zumkeller, Nov 15 2012

MATHEMATICA

Select[Range@ 192, ! IntegerQ@ Log2@ DivisorSigma[0, #] &] (* Michael De Vlieger, Feb 24 2017 *)

PROG

(Haskell)

a162643 n = a162643_list !! (n-1)

a162643_list = filter ((== 0) . a209229 . a000005) [1..]

-- Reinhard Zumkeller, Nov 15 2012

CROSSREFS

A000005.

Sequence in context: A094120 A066423 A072498 * A072587 A240112 A162645

Adjacent sequences:  A162640 A162641 A162642 * A162644 A162645 A162646

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 08 2009

STATUS

approved

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Last modified February 16 08:26 EST 2019. Contains 320159 sequences. (Running on oeis4.)