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I'm writing some equations dealing with sets and sequences.

I have a sequence $S$ and want to show that $x$ is an element of $S$, however I am hesitant writing $x \in S$ because I don't want to indicate $S$ is a set. I would also prefer not to write 'substring of length one' (e.g. $\hat{x} \subseteq S$, or something to that effect) because x should not be mistaken for a sequence either.

What is the best notation for 'element of a sequence'?

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    Conventional is to call the sequence $(s_k)$ and to denote an individual entry by $s_k$. I agree that "element" is not good.2012-08-23
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    Suppose I am the offspring of blasphemous computer scientists who never write $(s_k)$? :)2012-08-23
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    Are "words" not acceptable? I'd say that $x$ appears in $S$.2012-08-23
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    Parents know best: ask them. I even wrote a few papers in theoretical computer science, but used conventional mathematical notation. There was no apparent outrage.2012-08-23
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    Would something like $\exists i: S_i=x$ be acceptable?2012-08-23
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    @Thomas: I'm not sure I get the point about never writing $(s_k)$. Though I'm not a computer scientist, I wouldn't either, but I would freely write $S=(s_k)_{k\in\mathbf N}$.2012-08-23
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    If you don’t care about the index and are only interested in the fact that $x$ is a term of $S$, you can take advantage of the fact that a sequence is a function and write $x\in\operatorname{ran}S$.2012-08-23
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    Okay... I should not have said that some people 'never write $(s_k)$'! I will write it like that, using $S = (s_k)_{k \in \mathbb{N}}$ when necessary.2012-08-23

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