A076231 Numbers k such that sigma(k)/k, sigma_3(k)/k and sigma_5(k)/k are all integers.

1, 6, 120, 672, 8128, 30240, 32760, 33550336, 459818240, 1379454720, 1476304896, 8589869056, 31998395520, 51001180160, 66433720320, 137438691328, 153003540480, 403031236608, 30823866178560, 796928461056000, 6088728021160320, 14942123276641920, 212517062615531520

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..86

Prog

(PARI) isok(n) = !(sigma(n) % n) && !(sigma(n, 3) % n) && !(sigma(n, 5) % n); \\ Michel Marcus, Dec 26 2013

Crossrefs

Intersection of A007691, A046763 and A055709.

Cf. A000203, A001158, A001160, A007691, A046763, A055709, A076233, A076234.

Sequence in context: A076233 A066581 A054776 * A076234 A066289 A351862

Adjacent sequences: A076228 A076229 A076230 * A076232 A076233 A076234

Keyword

nonn

Author

Labos Elemer, Oct 03 2002

Extensions

a(16)-a(20) from Donovan Johnson, May 08 2010

a(21)-a(23) from Amiram Eldar, May 09 2024

Status

approved