[seqfan] A180634
israel at math.ubc.ca
israel at math.ubc.ca
Tue Dec 9 01:11:13 CET 2014
A180634 is "Numbers n such that the discriminant of the n-th cyclotomic
polynomial is a square". It appears to also coincide with n such that the
product of elements in the group of invertible elements mod n (i.e. the
product mod n of x such that 1 <= x < n and x is coprime to n) is 1. Is
this true? An equivalent characterization of the latter (apart from n=2): n
such that the number of square roots of 1 mod n is divisible by 4.
Cheers,
Robert
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