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A279039 Odd numbers n such that 2^n == 1 (mod sigma(n)). 1
1, 25, 52606009, 1088670025, 1315150225 (list; graph; refs; listen; history; text; internal format)
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 A116197 A023924

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 October 16 05:56 EDT 2019. Contains 328046 sequences. (Running on oeis4.)