login
A068378
Numbers n such that sigma(n)^2 > 9*sigma_2(n) where sigma_2(n) is the sum of squares over the divisors of n.
1
5040, 7560, 10080, 12600, 13860, 15120, 17640, 18480, 20160, 21840, 22680, 25200, 27720, 30240, 32760, 35280, 36960, 37800, 39600, 40320, 41580, 42840, 43680, 45360, 46200, 47520, 47880, 49140, 50400, 51480, 52920, 54600, 55440, 56160
OFFSET
1,1
LINKS
MATHEMATICA
Select[Range[60000], DivisorSigma[1, #]^2>9DivisorSigma[2, #]&] (* Harvey P. Dale, Mar 20 2015 *)
PROG
(PARI) for(n=1, 1000, if(sigma(n)^2>9*sumdiv(n, k, k^2), print1(n, ", ")))
CROSSREFS
Sequence in context: A290121 A269125 A111030 * A036458 A190107 A090393
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 04 2002
STATUS
approved