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A069059 Numbers n such that n and sigma(n) are not relatively prime. 8
6, 10, 12, 14, 15, 18, 20, 22, 24, 26, 28, 30, 33, 34, 38, 40, 42, 44, 45, 46, 48, 51, 52, 54, 56, 58, 60, 62, 66, 68, 69, 70, 72, 74, 76, 78, 80, 82, 84, 86, 87, 88, 90, 91, 92, 94, 95, 96, 99, 102, 104, 105, 106, 108, 110, 112, 114, 116, 117, 118, 120, 122, 123, 124 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Complement of A014567(n).

A009194(a(n)) > 1. - Reinhard Zumkeller, Mar 23 2013

Also, numbers n such that the reduced denominator of Sum_{d|n} 1/d (A017666) is less than n. - Ivan Neretin, Aug 30 2015

LINKS

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

MAPLE

select(n -> igcd(n, numtheory:-sigma(n)) > 1, [$1..1000]); # Robert Israel, Sep 01 2015

MATHEMATICA

Select[Range@125, GCD[#, DivisorSigma[1, #]] > 1 &] (* Ivan Neretin, Aug 30 2015 *)

PROG

(PARI) for(n=1, 160, if(gcd(sigma(n), n)>1, print1(n, ", ")))

(Haskell)

a069059 n = a069059_list !! (n-1)

a069059_list = filter ((> 1) . a009194) [1..]

-- Reinhard Zumkeller, Mar 23 2013

CROSSREFS

Cf. A009194, A014567, A017666.

Sequence in context: A325281 A100658 A182301 * A273157 A139587 A201463

Adjacent sequences:  A069056 A069057 A069058 * A069060 A069061 A069062

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 04 2002

STATUS

approved

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Last modified November 20 12:13 EST 2019. Contains 329335 sequences. (Running on oeis4.)