Describe all nonisomorphic central extensions of Z_2 x Z_2 by a cyclic group Z_n for arbitrary n, meaning central extensions of the form:
1 --> Z_n --> G --> Z_2 x Z_2 --> 1
There is a theorem stating that for an extension like this:
If H is an abelian group then all the extensions can be found through analyzing the second homologies in the form of H^2(M, H).
We also know that if m and n are relatively prime then Z_m x Z_n= Z_(mxn).
Well, now we want G such ...
Nonisomorphic central extensions are described.