OFFSET
1,2
COMMENTS
The corresponding integers are in A238502.
Includes all the primes and all the squarefree semiprimes (A006881). - Amiram Eldar, Nov 03 2024
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MATHEMATICA
lst={}; f[n_]:=DivisorSigma[1, n]/Plus@@Select[Divisors@n, #<=Sqrt@n&]; Do[If[IntegerQ[f[n]], AppendTo[lst, n]], {n, 1, 200}]; lst
PROG
(PARI) is(k) = if(k == 1, 1, my(f = factor(k)); !(sigma(f) % sumdiv(f, d, d * (d^2 <= k)))); \\ Amiram Eldar, Nov 03 2024
CROSSREFS
KEYWORD
nonn,changed
AUTHOR
Michel Lagneau, Mar 11 2014
STATUS
approved