The following should work:
Code:
program:
test(
field('series'),
strcat('__Series__/',field('series'),'/',format_number(field('series_index'),'{0:02d}'),' - ',field('title'),' - ',field('author_sort')),
strcat(substr(field('author_sort'),0,1),'/',field('author_sort'),'/',field('title'))
)
I have to say it is ugly.