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A069168 Numbers n such that sigma(n)*sum(d|n,1/sigma(d)) is not an integer. 0
4, 8, 9, 12, 16, 20, 24, 25, 27, 32, 36, 44, 45, 48, 49, 50, 54, 56, 60, 63, 64, 68, 72, 75, 80, 81, 88, 92, 96, 98, 99, 100, 104, 108, 112, 116, 117, 121, 125, 128, 132, 135, 136, 144, 147, 150, 153, 160, 162, 164, 168, 169, 171, 175, 176, 180, 184, 188, 189, 192 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A proper subset of A013929. - Robert G. Wilson v, Jul 21 2012

LINKS

Table of n, a(n) for n=1..60.

MATHEMATICA

fQ[n_] := !IntegerQ[ DivisorSigma[1, n] Plus @@ (1/DivisorSigma[1, Divisors[n]])]; Select[ Range@ 200, fQ] (* Robert G. Wilson v, Jul 21 2012 *)

CROSSREFS

Sequence in context: A057109 A069189 A283050 * A102211 A244032 A321454

Adjacent sequences:  A069165 A069166 A069167 * A069169 A069170 A069171

KEYWORD

easy,nonn

AUTHOR

Benoit Cloitre, Apr 09 2002

STATUS

approved

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Last modified March 20 20:14 EDT 2019. Contains 321352 sequences. (Running on oeis4.)