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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. 2
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 (list; graph; refs; listen; history; text; internal format)
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: A252961 A252962 A296767 * 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

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Last modified September 16 10:36 EDT 2019. Contains 327094 sequences. (Running on oeis4.)