Interlocking interval topology

The open sets in this topology are taken to be the whole set S, the empty set ∅, and the sets generated by

${\displaystyle X_{n}:=\left(0,{\frac {1}{n}}\right)\cup (n,n+1)=\left\{x\in {\mathbf {R} }^{+}:0<x<{\frac {1}{n}}\ {\text{ or }}\ n<x<n+1\right\}.}$

The sets generated by X_n will be formed by all possible unions of finite intersections of the X_n.^[2]

• List of topologies

• Steen, Lynn Arthur; Seebach, J. Arthur Jr. (1978). Counterexamples in Topology (2nd ed.). Berlin, New York: Springer-Verlag. ISBN 3-540-90312-7. MR 0507446. Zbl 0386.54001.