Is this a power signal?
There a few variations on the definitions of "energy signal" and "power signal". For example, Sklar in his textook "Digital Communications" defines "energy signal" as a signal with energy $E$ such that $0 &lt; E &lt; \infty$, and a "power signal" as a signal with power $P$ such that $0 &lt; P &lt;\infty$.

However, others (see for example this answer) define "energy signal" as a signal with $E &lt; \infty$.

In your case, $x[n]=0$ for all $n$; then this signal has zero energy and zero power. Whether it is classified as an energy or a power signal depends on which specific definition you adopt. For instance, if you go with Sklar's, then this signal is neither an energy signal nor a power signal.