A023198 Numbers k such that sigma(k) >= 4*k.

27720, 30240, 32760, 50400, 55440, 60480, 65520, 75600, 83160, 85680, 90720, 95760, 98280, 100800, 105840, 110880, 115920, 120120, 120960, 128520, 131040, 138600, 141120, 143640, 151200, 163800, 166320, 171360, 176400, 180180, 181440, 184800

Offset: 1

Author

David W. Wilson

Keywords

• nonn

Comments

Called 4-abundant numbers. The first odd number is A119240(4) = 1853070540093840001956842537745897243375. - T. D. Noe, Mar 31 2011

References

• Melvyn B. Nathanson, Elementary Methods in Number Theory, Springer, 2000, p 260.

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (terms 1..1000 from T. D. Noe)

Crossrefs

Union of A027687 and A068404.

Programs

Mathematica

Select[Range[1000000], DivisorSigma[1, #] >= 4*#&] (* Vladimir Joseph Stephan Orlovsky, Apr 21 2010 *)