A total of 19 sites are hosted on 23.43.121.241.
Here are the first 5 as they would appear when searched for:
last.fm/user/ridsevilla
(null)
last.fm/user/pikamaster13
(null)
lastfm.pl/user/paullaaaa
(null)
last.fm/user/keygen
(null)
last.fm/user/JM_Beaubourg
(null)
...and the list of the remaining 14:
last.fm/user/spLiFF22
last.fm/user/beyondwithin
lastfm.pl/user/netherbound
lastfm.com.br/user/lucas_alvim
lastfm.es/user/markitish
lastfm.pl/user/Fallstad
lastfm.pl/user/netversed
last.fm/user/dorrubin
last.fm/user/Slow2die
last.fm/user/tool9988
lastfm.fr/user/MRNSR
lastfm.de/user/sahnehering
lastfm.es/user/Noobiex
last.fm/user/bibowns