OFFSET
1,1
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]);
t:= a mod b; if not isprime(t) then return false fi;
c:= numtheory:-sigma(n);
a mod c = t
end proc:
select(filter, [$2..2*10^7]);
MATHEMATICA
Select[Range[2*10^6], (r = Mod[#*(# + 1)/2, DivisorSigma[1, #]]) == Mod[#*(# + 1)/2, Plus @@ Times @@@ FactorInteger[#]] && PrimeQ[r] &] (* Amiram Eldar, Apr 15 2022 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
J. M. Bergot and Robert Israel, Apr 15 2022
EXTENSIONS
a(8) from Amiram Eldar, Apr 15 2022
a(9)-a(10) from Daniel Suteu, May 12 2022
STATUS
approved