A067766 Numbers n such that sigma(n)^2>4*sigma_2(n) where sigma_2(n) is the sum of squares over the divisors of n.

24, 36, 48, 60, 72, 84, 90, 96, 108, 120, 126, 132, 140, 144, 150, 156, 160, 168, 180, 192, 204, 210, 216, 228, 240, 252, 264, 270, 276, 280, 288, 300, 312, 320, 324, 330, 336, 360, 378, 384, 390, 396, 400, 408, 420, 432, 440, 450, 456, 462, 468, 480, 504

Offset

1,1

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Mathematica

Select[Range[600], DivisorSigma[1, #]^2>4*DivisorSigma[2, #]&] (* Harvey P. Dale, Dec 27 2015 *)

Prog

(PARI) for(n=1, 1000, if(sigma(n)^2>4*sumdiv(n, k, k^2), print1(n, ", ")))

Crossrefs

Sequence in context: A054775 A273088 A334674 * A376445 A306776 A300794

Adjacent sequences: A067763 A067764 A067765 * A067767 A067768 A067769

Keyword

easy,nonn

Author

Benoit Cloitre, Apr 04 2002

Status

approved