OFFSET
1,2
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..10000
MATHEMATICA
Select[Range[50000], IntegerQ[DivisorSigma[2, #]/(DivisorSigma[1, #] DivisorSigma[ 0, #])]&] (* Harvey P. Dale, Feb 12 2013 *)
PROG
(PARI) isok(k) = denominator(sigma(k, 2)/(sigma(k, 1)*sigma(k, 0))) == 1; \\ Michel Marcus, Jul 15 2019
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Ctibor O. Zizka, Nov 29 2008
EXTENSIONS
More terms from Harvey P. Dale, Feb 12 2013
STATUS
approved