OFFSET
1,2
LINKS
Giovanni Resta, Table of n, a(n) for n = 1..41 (terms < 5*10^12)
EXAMPLE
For k = 6066396, sigma_2(k)/k = 9156979, sigma_4(k)/k = 241153415598179286943.
MATHEMATICA
Select[Range[10^7], And @@ Divisible[DivisorSigma[{2, 4}, #], #] &] (* Amiram Eldar, Jan 20 2020 *)
PROG
(PARI) isok(n) = !(sigma(n, 2) % n) && !(sigma(n, 4) % n); \\ Michel Marcus, Aug 28 2019
(Magma) [n: n in [1..10000000]|IsIntegral(DivisorSigma(2, n)/n) and IsIntegral(DivisorSigma(4, n)/n)]; // Marius A. Burtea, Aug 28 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 03 2002
EXTENSIONS
More terms from T. D. Noe, Apr 11 2006
a(11)-a(12) from Michel Marcus, Aug 28 2019
a(13)-a(18) from Amiram Eldar, Jan 20 2020
a(19)-a(24) from Giovanni Resta, Jan 21 2020
STATUS
approved