[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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