List Items

Hello,

I have 800 items (number of breps - bricks - in a brick wall).

i want to select item numbers 40-79, 120-159, 200-239, 280-319, 320-359, 400-439...

In short the logic is: i do not want to extract 1st 40 items - then i want to extract next 40 - then i do not want next 80 - after that i want subsequent 40 - the sequence goes on until i reach 800.

i can use series. but i will have to use series many times before i merge them to form sequential list of numbers.

is there a simpler mathematical way?

Regards,

Agneesh