Expression 1: Start sum from "n" equals 1 to "x" , end sum, left parenthesis, left brace, mod left parenthesis, round left parenthesis, "x" , right parenthesis , "n" , right parenthesis equals 0 : "n" , 0 , right brace , right parenthesisx∑n=1modroundx,n=0:n,0