A279039 - OEIS

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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