OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..5000
EXAMPLE
a(4) = 14 is a term because A340180(14) = 23 is prime.
MAPLE
f:= proc(n) local s, k;
s:= numtheory:-sigma(n);
add(`if`(igcd(n, k)=1, s mod k, 0), k=1..n-1);
end proc:
select(t -> isprime(f(t)), [$1..1000]);
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Mar 17 2021
STATUS
approved