# Arrow up notation

I have a simple question about a notation that I found in a scientific paper. The authors use the following notation:

$[...] \hspace{0.5cm} d_n \uparrow \infty \hspace{0.2cm} \text{as} \hspace{0.2cm} n \rightarrow\infty. \hspace{0.5cm} [...]$

What could the authors possibly mean with the arrow that goes up? What happens to $d_n$ as n goes to infinity? When I was searching for an explanation, all I found was Knuth's arrow up. But the authors don't seem to use the arrow in that way.

I don't think that this is a typo, as the authors are quite renowned in their field of study, and the paper was published in the Journal of Econometrics.

Note: I think more context would only distract from the question at hand. If you disagree, I can provide more details.

It is an increasing (or non decreasing) sequence that goes to infinity. Some authors also use $\nearrow$