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A278337
Composite numbers n such that the sum of proper divisors of n divides 2^n+1.
0
15, 45, 99, 735, 1221, 1645, 1725, 1925, 2871, 4047, 8667, 13311, 16461, 19647, 21285, 27797, 39861, 52215, 52965, 65637, 67479, 74781, 106327, 124215, 126975, 155511, 181917, 240397, 244839, 257951, 315695, 344175, 412863, 442417, 445215, 449493, 707859, 1362079
OFFSET
1,1
COMMENTS
Are all terms odd? There are no even terms < 2*10^12.
MAPLE
select(n -> not isprime(n) and 2 &^n + 1 mod (numtheory:-sigma(n)-n) = 0, [$2..10^6]);
PROG
(PARI) is(n)=n>9 && !isprime(n) && Mod(2, sigma(n)-n)^n==-1 \\ Charles R Greathouse IV, Nov 18 2016
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel and Altug Alkan, Nov 18 2016
STATUS
approved