A218427 Numbers k for which sigma(k)/k - 4/5 is an integer.

10, 60, 1170, 114660, 72602880, 668304000, 714954240, 1307124000, 1381161600, 2701389600, 8052817920, 10181689600, 643773312000, 1330464844800, 2015156183040, 3522876144480, 15462510336000, 23885971200000, 702577007193600, 908714417345280

Offset

1,1

Comments

a(13) > 10^11. - Donovan Johnson, Oct 31 2012

a(14) > 10^12. - Giovanni Resta, Nov 04 2012

Links

Table of n, a(n) for n=1..20.

M. Drennen, T. Gunter, P. Johnson and J. Ward, The Loneliest Number

Jeffrey Ward, Does Ten Have a Friend?, arXiv:0806.1001 [math.NT], 2008.

Crossrefs

Cf. A218406, A218407, A218408.

Sequence in context: A219368 A052664 A090373 * A354944 A041184 A089034

Adjacent sequences: A218424 A218425 A218426 * A218428 A218429 A218430

Keyword

nonn

Author

Zdenek Cervenka, Oct 28 2012

Extensions

a(5)-a(12) from Donovan Johnson, Oct 31 2012

a(13) from Giovanni Resta, Nov 04 2012

More terms from Michel Marcus, Jun 26 2013

Status

approved