[chaley]

You can generate a list of books in a series (or any other column) with at least N books in the series with a template search. I felt like playing with it and here is a solution that works for me.

Steps:

1. Create a stored template (Preferences / Template functions / Stored templates).
   • The template name is 'count_books_with_same_field_value'. It can actually be what you want, but it must be a valid name and you must use this name below.
   • The template is
     

     python:
     def evaluate(book, context):
     	args = context.arguments
     	if args is None or len(args) != 2:
     		return 'Bad argument count. Must be 2 (column, count)'
     	
     	column = args[0]
     	min_count = int(args[1])
     
     	globals = context.globals
     	db = context.db.new_api
     
     	if globals is None or 'possibles' not in globals:
     		possibles = set()
     		id_count_map = db.get_usage_count_by_id(column)
     		for id,count in id_count_map.items():
     			if count >= min_count:
     				possibles.add(db.get_item_name(column, id))
     		globals['possibles'] = possibles
     
     	possibles = globals['possibles']
     	book_vals = db.field_for(column, book.id)
     
     	if not isinstance(book_vals, (tuple, list)):
     		book_vals = list((book_vals,))
     	for v in book_vals:
     		if v in possibles:
     			return '1'
     	return ''

   • Press the "Create" button to store the template.
   Here is a screen capture of the Stored template dialog.
   
2. Create a template search
   • Click the "Advanced search" icon in the search bar (a gear).
   • Choose "Template search"
   • Set the "Template value" to "True"
   • Set the "Comparison type" to "Set/Not set"
   • Set the "Template" to
     

     program: count_books_with_same_field_value('series', 4)

     where 'series' is the column lookup key you want to check, and '4' is the minimum count you want.
   • Here is a screen capture of the Template search dialog
     
3. Save the new template search as a saved search if you wish

For example, this template search:

template:"""program: count_books_with_same_field_value('series', 4)#@#:b:True"""

will produce a list of books in any series with at least 4 books.

Comparison of approaches:

• The techniques mentioned in the above posts do something similar, one item at a time. For example, sorting by count in the tag browser then clicking on a series with the count you wish will produce a list of books in that series.
• The template search approach described here produces a list of books in all series with at least the count you wish.

I can't say which technique works better for you.