Came up with this last night. Seemed to work well while doing subnetting practice questions. Also with a powers of 2 list but not really needed because block size is 1 more than wildcard. Really just need the powers of 2 for questions asking to make x number of subnets or some crazy number of hosts. Thought I would share. Each column is your octet place. So /18 would be netmask:255.255.192.0 and wildcard:0.0.63.255 because /18 is in the 3rd colum related to 192 and 63.