OFFSET
1,1
COMMENTS
69672960000 is also a term in the sequence.
a(7) <= 2704853606400. The numbers 242595672883200000, 66217181184000000000 and 185577469193591193600 are also terms. - Giorgos Kalogeropoulos, Jun 18 2024
4672651788288000 is also a term. - Jud McCranie, Jun 18 2024
The sequence is complete through 10^13. - Jud McCranie, Sep 14 2024
EXAMPLE
16 -> 30 -> 24 -> 16, so 16 (the smallest term) is in the sequence.
PROG
(PARI) isok(x) = my(y = eulerphi(sigma(x))); if (y > x, my(z = eulerphi(sigma(y))); if (z > x, x == eulerphi(sigma(z)))); \\ Michel Marcus, Jun 07 2024
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Jud McCranie, Jun 06 2024
EXTENSIONS
a(6) from Giorgos Kalogeropoulos, Jun 18 2024
STATUS
approved