I have updated one of my PowerShell Script - List Group Members in Active Directory–PowerShell Script – to generate a report and send an email based on number of members in an Administrator group on a server. I crated this script based on a question posted on the TechNet forum.
Input – This script reads server names from an input file called Serves.csv
Output - It creates an output file called SGroupMemberDetails.csv which contains all server and group information. It also generate an email alert based on number of group members. You can set this threshold value using $N variable.
Here are the script details