I don't believe that a regular expression is possible to dynamically set up the SSH configuration. However, you should be able to use a for loop in Bash to automatically create the three lines in the config file for each server. For this example, I will assume you need to create entries for servers pro-75 to pro-125.
for i in $(seq 75 125);
echo "Host pro-$i" >> ~/.ssh/config
echo "Hostname 192.168.1.$i" >> ~/.ssh/config
echo "ProxyCommand ssh production-server nc %h %p" >> ~/.ssh/config
echo "\n" >> ~/.ssh/config
This will build a list of all numbers from 75 to 125 and store that as the list for the loop. It then loops through each member of the list and replaces $i. Each line is appended to the end of the SSH user config file. Finally, I included the newline to break up the configuration file just a little bit.
If you have specific values which are needed on the list, rather than a contiguous segment of numbers, then build a list manually, like this:
1 23 45 67 89