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.

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

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Cf. A000203, A001157.

Sequence in context: A290121 A269125 A111030 * A036458 A190107 A090393

Adjacent sequences: A068375 A068376 A068377 * A068379 A068380 A068381

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 04 2002

Status

approved