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A023884 Average of divisors except itself is an integer. 5
2, 3, 5, 6, 7, 9, 11, 13, 15, 17, 19, 23, 25, 29, 30, 31, 33, 37, 41, 43, 44, 47, 49, 51, 53, 59, 61, 67, 69, 71, 73, 79, 81, 83, 87, 89, 91, 97, 101, 103, 107, 109, 113, 114, 117, 120, 121, 123, 124, 127, 131, 133, 135, 137, 139, 141, 149, 151, 157, 159 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

All the prime numbers (A000040) are in this sequence. But there are other numbers (A023885). - Daniel Lignon, Feb 26 2015

LINKS

Daniel Lignon, Table of n, a(n) for n = 1..1000

MATHEMATICA

Select[Range[2000], IntegerQ[Mean[Most[Divisors[#]]]]&] (* Daniel Lignon, Feb 26 2015 *)

PROG

(PARI) isok(n) = !((sigma(n) - n) % (numdiv(n)-1)); \\ Michel Marcus, Mar 01 2015

CROSSREFS

Sequence in context: A106843 A057165 A245395 * A135607 A026453 A026455

Adjacent sequences:  A023881 A023882 A023883 * A023885 A023886 A023887

KEYWORD

nonn

AUTHOR

Olivier Gérard

STATUS

approved

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Last modified November 13 19:25 EST 2018. Contains 317149 sequences. (Running on oeis4.)