OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..269 (terms up to 10^10)
EXAMPLE
For k = 20: sigma(k) = 42 ,sigma_2(k) = 546 = 13 * 42, sigma_3(k) = 9198 = 219 * 42, sigma_4(k) = 170898 = 4069 * 42, sigma_5(k) = 3304182 = 78671 * 42.
MATHEMATICA
Select[Range[2000000], And@@Divisible[DivisorSigma[Range[2, 5], #], DivisorSigma[ 1, #]]&] (* Harvey P. Dale, Jan 01 2012 *)
PROG
(PARI) is(k) = {my(f = factor(k), s = sigma(f)); for(k = 2, 5, if(sigma(f, k) % s, return(0))); 1; } \\ Amiram Eldar, Jun 15 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Aug 27 2002
STATUS
approved