Homotopy colimit of spectra ($\mathrm{hocolim}{T}_j$)

A homotopy colimit of spectra is the derived colimit of a diagram of topological spectra. For a sequential diagram $T_0\to T_1\to \cdots$, it is the cofiber of spectra of $1-s:{\bigvee }_j{T}_j\to {\bigvee }_j{T}_j$, where $s$ uses the bonding maps into the next summands.

For $D={\mathrm{hocolim}}_j{T}_j$, applying $[-,E{]}_{\mathrm{st}}$ to the telescope cofiber sequence of spectra givesHere ${\lim }^1$ is the cokernel of $1-r$ on the product of the inverse tower, where $r$ uses its bonding maps. This records the obstruction to uniqueness when compatible stage maps are realized.