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A279039
Odd numbers n such that 2^n == 1 (mod sigma(n)).
1
1, 25, 52606009, 1088670025, 1315150225
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OFFSET
1,2
LINKS
Table of n, a(n) for n=1..5.
EXAMPLE
25 is a term because it is an odd number and sigma(25) divides 2^25 - 1.
PROG
(PARI) is(n)=Mod(2, sigma(n))^n==1&&n%2==1;
CROSSREFS
Cf.
A000203
,
A000225
,
A278836
.
Sequence in context:
A196520
A228536
A191559
*
A237522
A347810
A116197
Adjacent sequences:
A279036
A279037
A279038
*
A279040
A279041
A279042
KEYWORD
nonn
,
more
AUTHOR
Altug Alkan
, Dec 04 2016
STATUS
approved
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Last modified May 19 14:45 EDT 2024. Contains 372698 sequences. (Running on oeis4.)