Go to Google and Google (do not use “I feel lucky!” because when does Larry ever get Lucky?) and search for:

exp(?(?(((x-?4)^?2+?(y-?4)^?2)^?2))/?1000)+?exp(?(?(((x+?4)^?2+?(y+?4)^?2)^?2))/?1000)+?0.15*?exp(??(((x+?4)^?2+?(y+?4)^?2)^?2))+?0.15*?exp(??(((x-?4)^?2+?(y-?4)^?2)^?2))

Just copy and paste it into google and search.

Or just let me Google that for you (though it takes a minute to type out the whole thing for you!)