Here is a sample of a the Robots.txt for WordPress that you may see on numerous sites..
# 1. A robot may not injure a web server or, through inaction, allow a web
# server to come to harm.
# 2. A robot must obey orders given it by web servers except where such
# orders would conflict with the First Law.
# 3. A robot must protect its own existence as long as such protection does
# not conflict with the First or Second Law.
Please keep in mind that identifying the location of the actual /wp-admin page will make it a candidate during the Global WordPress Attack.