A076234 Numbers k such that sigma(k)/k, sigma_3(k)/k, sigma_5(k)/k and sigma_7(k)/k are all integers.

1, 6, 120, 672, 30240, 32760, 33550336, 459818240, 1379454720, 8589869056, 31998395520, 51001180160, 137438691328, 153003540480, 30823866178560, 796928461056000, 6088728021160320, 212517062615531520, 2305843008139952128, 69357059049509038080, 143573364313605309726720

Offset

1,2

Links

Amiram Eldar, Table of n, a(n) for n = 1..55

Prog

(PARI) isok(n) = !(sigma(n) % n) && !(sigma(n, 3) % n) && !(sigma(n, 5) % n) && !(sigma(n, 7) % n); \\ Michel Marcus, Dec 26 2013

Crossrefs

Cf. A000203, A001158, A001160, A013955.

Cf. A007691, A046763, A055709, A076231, A076233.

Cf. A066289 (k divides sigma_m(k) for all odd m).

Sequence in context: A066581 A054776 A076231 * A066289 A351862 A170917

Adjacent sequences: A076231 A076232 A076233 * A076235 A076236 A076237

Keyword

nonn

Author

Labos Elemer, Oct 04 2002

Extensions

a(13)-a(18) from Donovan Johnson, May 08 2010

a(19)-a(21) from Amiram Eldar, May 09 2024

Status

approved