Labyrinth Seal Leakage Calculation ?

[FFX]

I'm studying mechanical engineering, just have a question on the labyrinth seal leakage equation.

More specifically, the expansion ratio formula.

What does the '1n' stand for?
With 'n + 1n', I'm assuming those two n's are different since one looks like it's in italics and the other looks normal. Can someone please clear this up for me? I understand the rest of the equation, I just can't find what '1n' stands for in my textbook.

 

[gneill]

I'm studying mechanical engineering, just have a question on the labyrinth seal leakage equation.

More specifically, the expansion ratio formula.

What does the '1n' stand for?
With 'n + 1n', I'm assuming those two n's are different since one looks like it's in italics and the other looks normal. Can someone please clear this up for me? I understand the rest of the equation, I just can't find what '1n' stands for in my textbook.

Perhaps it's meant to be the natural log function ln(x)? That's the log base e of its argument.