OFFSET
1,1
COMMENTS
Includes 1+A000668.
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
a(3) = 18 is in the sequence because sigma(18) = 39, 39 == 3 (mod 18), and 3 is prime.
MAPLE
select(n -> isprime(numtheory:-sigma(n) mod n), [$2..1000]);
PROG
(PARI) isok(n) = isprime(sigma(n) % n); \\ Michel Marcus, May 15 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, May 14 2019
STATUS
approved