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A110817 Numbers n such that (1/n)sigma(n+1) is an integer. 2
1, 2, 9, 135, 32895, 2147516415 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

These are all the terms up to 10^8.

LINKS

Table of n, a(n) for n=1..6.

EXAMPLE

sigma(2+1)/2 = 2, so 2 is a term of the sequence.

MAPLE

A110817:=proc(q)

local n;

for n from 1 to q do if (sigma(n+1) mod n)=0 then print(n); fi; od; end:

A110817 (10000000000); # Paolo P. Lava, Feb 26 2013

MATHEMATICA

Select[Range[10^6], IntegerQ[DivisorSigma[1, # + 1]/# ] &]

CROSSREFS

Sequence in context: A295331 A064448 A173215 * A189428 A110860 A050995

Adjacent sequences:  A110814 A110815 A110816 * A110818 A110819 A110820

KEYWORD

nonn

AUTHOR

Joseph L. Pe, Sep 15 2005

EXTENSIONS

a(6) from Donovan Johnson, Nov 15 2009

STATUS

approved

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Last modified June 20 00:47 EDT 2019. Contains 324223 sequences. (Running on oeis4.)