Apparently bought in two chunks: 3.0.0.0/9 and 3.128.0.0/9.
Previous owner was GE.
Anecdotal reports across the Internet that AWS EIPs are now being assigned in that range.
https://whois.arin.net/rest/net/NET-3-0-0-0-1.html
https://whois.arin.net/rest/net/NET-3-128-0-0-1.html
http://maps.measurement-factory.com/
It's a great purchase for them, and a shot at Azure and GCP - Amazon can now legitimately tell larger clients "we will have enough IPv4 space to be your partner for all your static-IP-dependent applications, no matter how much you need to scale."