OFFSET
1,1
COMMENTS
Terms are listed in the order in which they appear in A340180, including repetitions.
Repeated terms include a(1) = a(2) = 2, a(55) = a(56) = 17333, and a(233) = a(319) = 1253761. Are there any others?
LINKS
Robert Israel, Table of n, a(n) for n = 1..5000
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(isprime, map(f, [$1..1000]));
MATHEMATICA
Select[Array[Sum[Mod[DivisorSigma[1, #], k] Floor[1/GCD[k, #]], {k, # - 1}] &, 500], PrimeQ] (* Michael De Vlieger, Mar 17 2021 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Mar 17 2021
STATUS
approved