A023884 - OEIS

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A023884

Average of divisors except itself is an integer.

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

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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

MAPLE

q:=n->(irem(numtheory[sigma](n)-n, numtheory[tau](n)-1)=0):

select(q, [$2..159])[]; # Lorenzo Sauras Altuzarra, Feb 01 2023

MATHEMATICA

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