Set Definition by Predicate/Examples/Set Indexed by Natural Numbers between 1 and 10

Examples of Set Definition by Predicate
Let $U$ be the set defined as:
 * $U := \set {u_i: 1 < i < 10, i \in \N}$

Then $U$ has exactly $8$ elements:
 * $U = \set {u_2, u_3, u_4, u_5, u_6, u_7, u_8, u_9}$