Notation to describe that a value is equivalent to at least one component of a vector? Suppose I have the vector $X=<1, 2, 3, 4, 5, 1>$.  This notation should mean that this is a vector whose respective components are 1, 2, 3, 4, 5, and 1, in that same order.  Suppose I want to show that the value 1 is equivalent to at least one of the values of the component in the vector.
This seems similar to showing that an element is a member of a set, but clearly it's not exactly the same since the vector's components are not guaranteed to be distinct, as is in the case of a set.  So I can't use the "member of" ($1\in X$) notation.  So is there any appropriate notation for what I'm trying to show?

Define $U_a$ as the union of the hyper planes $H_i(a)$ where $x_i=a$ $$U_a=\cup_{i=1}^{n}H_i(a)$$
Then you can say $X \in U_1$ for what you are looking for. 
Unfortunately, I don’t know any pre-existing standard notation for this. 
