OFFSET
1,2
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..1000
MATHEMATICA
Select[Range[500], Divisible[DivisorSigma[1, DivisorSigma[1, DivisorSigma[ 1, #]]], DivisorSigma[ 1, #]]&] (* Harvey P. Dale, Oct 04 2017 *)
PROG
(PARI) { n=0; for (m=1, 10^10, if (sigma(sigma(sigma(m))) % sigma(m) == 0, write("b067064.txt", n++, " ", m); if (n==1000, return)) ) } \\ Harry J. Smith, May 02 2010
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Feb 17 2002
STATUS
approved