Create a boolean array " prime [ 0 . . n ] " and initialize all entries it as true . A value in prime [ i ] will finally be false if i is Not a prime , else true .
prime = [ True for i in range ( n + 1 ) ] NEW_LINE for p in range ( 2 , n + 1 ) : NEW_LINE INDENT if p * p > n : NEW_LINE INDENT break NEW_LINE DEDENT DEDENT