# is just octothorpe far's I know. Going a-googling I find 121 hits for anoctothorpe and 19,100 for octothorpe. Among the most authoritative of the latter I submit for your consideration:

http://www.worldwidewords.org/weirdwords/ww-oct1.htm

Weighing in for the former what looks like the best is this from the snopes message board (Useless fact [sic] #94) and it's none too supportive if you read on down the replies:

http://msgboard.snopes.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=47;t=000401;p=1