A218406 Numbers k for which sigma(k)/k - 1/5 is an integer.

5, 420, 7440, 8190, 18600, 121920, 131040, 95472000, 102136320, 197308800, 433305600, 503255040, 71271827200, 91967616000, 128848035840, 190066406400, 287879454720, 354560976000, 799959888000, 2061580369920, 2208930048000, 100368143884800, 341546502528000

Offset: 1

Author

Zdenek Cervenka, Oct 28 2012

Keywords

• nonn

Comments

a(15) > 10^11. - Donovan Johnson, Oct 31 2012

a(20) > 10^12. - Giovanni Resta, Nov 04 2012

Note that there are no terms here with abundancy 11/5 (k=2). - Michel Marcus, Jun 26 2013

Crossrefs

Cf. A218407, A218408, A218427.

Extensions

a(8)-a(14) from Donovan Johnson, Oct 31 2012

a(15)-a(19) from Giovanni Resta, Nov 04 2012

More terms from Michel Marcus, Jun 26 2013