|
| |
|
|
A220169
|
|
Numbers n for which phi(n^2) = phi(n-1) * phi(n+1).
|
|
0
|
|
|
|
2, 4, 16, 256, 976, 3256, 5188, 11716, 13366, 22936, 65536, 307396, 491536, 589408, 983776, 1659586, 2822716, 3137356, 5577826, 6475456, 7378372, 8698096, 10798726, 32235736, 37797436, 39220126, 39285436, 51555136, 52077196, 56992552, 63767926, 70075996, 82391002
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
|
OFFSET
|
1,1
|
|
|
LINKS
|
|
|
|
EXAMPLE
|
phi(976^2) = 468480 = 480*976 = phi(975)*phi(977).
|
|
|
MATHEMATICA
|
Select[Range[10^6], EulerPhi[#^2] == EulerPhi[# - 1] EulerPhi[# + 1] &]
|
|
|
PROG
|
(PARI) isok(n) = eulerphi(n^2) == eulerphi(n-1) * eulerphi(n+1); \\ Michel Marcus, Aug 12 2019
|
|
|
CROSSREFS
|
|
|
|
KEYWORD
|
nonn
|
|
|
AUTHOR
|
|
|
|
EXTENSIONS
|
|
|
|
STATUS
|
approved
|
| |
|
|
