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A319314
Numbers k such that 2^phi(k) == phi(k)^2 (mod k^2).
0
1, 3, 4, 5, 6, 8, 10, 12, 384, 640, 768, 896, 960, 24576, 49152, 950272, 1425408, 1572864, 3145728, 10485760, 19398656, 65011712, 100663296, 110057537, 201326592, 220115074, 671088640, 1879048192
OFFSET
1,2
COMMENTS
Sequence is infinite, i.e., 3*2^(3*(t-1)-(-1)^t) is a term for all t > 0.
Prime terms (5, 110057537, ...) are in A246568 based on case A = +1.
PROG
(PARI) isok(n) = Mod(2, n^2)^eulerphi(n)==eulerphi(n)^2;
(Magma) [1] cat [n: n in [1..10^6] | 2^EulerPhi(n) mod n^2 eq EulerPhi(n)^2]; // Vincenzo Librandi, Sep 20 2018
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Altug Alkan, Sep 17 2018
STATUS
approved