A096490 Numbers k such that sigma_2(k) >= 3/2 k^2, where sigma_2(x) is the sum of the squares of the divisors of x.

60, 120, 168, 180, 240, 252, 300, 336, 360, 420, 480, 504, 540, 600, 660, 672, 720, 756, 780, 792, 840, 900, 924, 936, 960, 1008, 1020, 1080, 1140, 1176, 1200, 1260, 1320, 1344, 1380, 1440, 1500, 1512, 1560, 1584, 1620, 1680, 1740, 1764, 1800, 1848, 1860

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Example

n=60: 1+4+9+16+25+36+100+144+225+400+900+3600=5460>1.5*3600=5400

Mathematica

Do[s=DivisorSigma[2, n]/(n^2); If[Greater[s, 3/2], Print[n]], {n, 1, 10000}]
Select[Range[2000], DivisorSigma[2, #]/#^2>=3/2&] (* Harvey P. Dale, Mar 05 2013 *)

Prog

(PARI) is(n)=sigma(n, -2) >= 3/2 \\ Charles R Greathouse IV, Feb 03 2018

Crossrefs

Cf. A001157, A056866.

Sequence in context: A252962 A296767 A336442 * A056866 A098136 A060793

Adjacent sequences: A096487 A096488 A096489 * A096491 A096492 A096493

Keyword

nonn

Author

Labos Elemer, Jun 25 2004

Extensions

Name corrected by Charles R Greathouse IV, Feb 03 2018

Status

approved