Hello! Please help!

I have a column with 20 integers, from 1 to 20. Each integer is
associated with a value in a second column.

These integers represent 20 evenly spaced points along a circle.
Points 1 and 20 are therefore close together, whereas points 1 and 10
are maximally separated.

I need to calculate the difference between the recorded values for
every possible combination of lag distances! Namely,
points with a lag distance of 1 would include (1,2) (2,3) (3,4)
(4,5) ... (20,1)
points with a lag distance of 2 would include (1,3) (2,4) (3,5) (4,6)
(5,7) ... (20,2)
points with a lag distance of 10 (maximal distance!) would include
(1,10) (2,11) (3,12) (4,13) ... (20,10)

I need to present all the calculated differences of my recorded values
in a new column. For each calculated difference I would also need to
know which lag I'm dealing with (1,2, ... 10), perhaps in another
column.

Thank you!

Ilford