Italics in plot main title

Hi,

I am drawing several plots and want to have italics in a main title;
this is easy with expression(). However, I want also to add a value to
it, say n_i, that depends on an ith plot. For this I am using paste().
An example: n_i = 10, 20, 30; I want to draw a plot for each i with
the title: "Relative efficiency for sample size n = n_i", where n
should be in italics, and of course n_i is not specified by value. The
expression() does not work with paste(). I know this might be easy,
but can't figure anything, so any ideas how this could be efficiently
done?

Thanks in advance,
Marcin