A sequential topological space $X$ has a few different equivalent definitions:
- $X$ is the quotient of a first-countable space
- $X$ is the quotient of a metric space
- Sequentially open subsets of $X$ are open
- Sequentially closed subsets of $X$ are closed
- For every subset of $X$ that is not closed, there is a convergent sequence to a point outside the subset
- Any sequentially continuous function from $X$ to another space is continuous
- The topology is the final topology with regards to all continuous maps from the one-point compactification of $\mathbb{N}$, i.e. convergent sequences in $X$, so those generate the topology
The Wikipedia article on sequential spaces claims that the spectrum of any noetherian ring is sequential. It does not provide a reference for this, is there one? Alternatively, is there a short proof of this statement? The most straightforward translation to a purely topological statement would be whether sober noetherian spaces are sequential.