is the only member here whose nickname can be expressed in the exponential form 7^x, where x can be any integer greater than or equal to 2. Why not 1, you ask? Well, because 7^1 equals 7 and Sevens' nickname is plural and implies more than one seven is needed. Likewise, x cannot be 0 or a negative number as 7^0 equals 1 and 7^-x would equal 1 divided by 7^x, which is far from 7, let alone several 7s.