Valid IP Octets include: 1-9 & 11-223, then 0-255, twice, then 1-254 but with no leading zeroes.
This will exclude the 10.0.0/8 private IP range, the reserved and multi-cast range, 224.0.0.0 and up, as well as the private IP ranges 172.16.0.0/12 and 192.168.0.0/16.
In other words, this will address all publicly accessible IPv4 addresses from 1.0.0.1 through 223.255.255.254.