I would like
a text editor able to control lines in special ways.
By example :
1. Maintain lines 1,5,9,13,17,21, and so on until the final of the txt file.
That is a aritmetic progression of reason equal to 4, where the first is 1.
Delete the rest of lines.
2. Any other criteria over the lines.
Note : i am only looking now for the 1. . It's the important case to me now.
Happy New Year