OFFSET
1,1
LINKS
Robert Israel, Table of n, a(n) for n = 1..10000
EXAMPLE
MAPLE
filter:= proc(n) local a, b, c, t;
a:= n*(n+1)/2;
b:= add(t[1]*t[2], t=ifactors(n)[2]);
if not isprime(a mod b) then return false fi;
c:= numtheory:-sigma(n);
isprime(a mod c)
end proc:
select(filter, [$2..3000]);
MATHEMATICA
Select[Range[3000], And @@ PrimeQ[Mod[#*(# + 1)/2, {DivisorSigma[1, #], Plus @@ Times @@@ FactorInteger[#]}]] &] (* Amiram Eldar, Apr 15 2022 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert Israel, Apr 14 2022
STATUS
approved