OFFSET
1,1
EXAMPLE
MAPLE
f:= n -> n + n*numtheory:-phi(n)/2 + numtheory:-sigma(n):
g:= proc(n) local t;
igcd(t[2], t=ifactors(n)[2]) > 1
end proc:
select(t -> g(f(t)), [$2..2*10^6]);
MATHEMATICA
ppQ[n_] := GCD @@ FactorInteger[n][[;; , 2]] > 1; Select[Range[10^7], ppQ[# + DivisorSigma[1, #] + #*EulerPhi[#]/2] &] (* Amiram Eldar, Apr 07 2022 *)
CROSSREFS
KEYWORD
nonn,more
AUTHOR
J. M. Bergot and Robert Israel, Apr 06 2022
STATUS
approved