How to read this mathematical expression

Question

The equation is of the form as given in the Image

Answer 1

I assume you found this image somewhere. To decipher it you really need the context.

$t_i$ is something like the set of all values $lpj$ for $j$ in the range from $1$ to $i$ and $l$ in the range from some unspecified starting point to $j \lfloor p_1/p_j \rfloor$, where $\lfloor \rfloor$ is the floor function that rounds down to the nearest integer.

It's hard to know for sure, since some obvious subscripts are missing. Perhaps $lpj$ needs them.