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A076233
Numbers k such that sigma(k)/k and sigma_3(k)/k are both integers.
4
1, 6, 120, 496, 672, 8128, 30240, 32760, 523776, 23569920, 33550336, 459818240, 1379454720, 1476304896, 8589869056, 31998395520, 51001180160, 66433720320, 137438691328, 153003540480, 403031236608, 30823866178560, 796928461056000, 6088728021160320, 14942123276641920
OFFSET
1,2
LINKS
PROG
(PARI) isok(n) = !(sigma(n) % n) && !(sigma(n, 3) % n); \\ Michel Marcus, Dec 26 2013
KEYWORD
nonn
AUTHOR
Labos Elemer, Oct 04 2002
EXTENSIONS
a(19)-a(25) from Amiram Eldar, May 09 2024
STATUS
approved