It is suggested that you use Python instead of Shell to manipulate text files!!

Besides passing an unsigned integer as parameter to the option -n, you can also pass a signed integer to it. When a signed integer is passed to -n, it means from/to (inclusive/exclusive similar to most programming languages) the row with this index (1-based). More specifically, head -n +/-k means take rows 1 (inclusive) to +/-k (exclusive). tail -n +/-k means take rows +/-k (inclusive) to the last row. Below are some examples to help you fruther understand how it works.

1. Print all but the last 5 lines.

   # -5 means without the last 5 lines  
   head -n -5 file_name
   

2. Print lines 6 and after (i.e., all but the first 5 lines).

   # +6 means starting from line 6  
   tail -n +6 file_name
   

3. Print lines 10 to 20.

   head -n 20 file_name | tail -n +10  
   # or you can use (11 = 20 - 10 + 1)
   tail -n +10 file_name | head -n 11
   

   Please refer to Print Rows from a Text File for better ways using sed and awk.