Algorithm - sequence 2 numbers

[Guest]

Hi, I need a mathematic algorithm only (not code) to solve the follow scenario:
Quantity of the items, from 1 to 200.
Quantity of the validation (checking), from 1 to 6 for each validation
Goal: to get the 2-sequence numbers - always a pair.
Example: (1-200) Items: 4
(3 checks) Item #1 / Checking: 3
(1 check ) Item #2 / Checking: 1
(4 checks) Item #3 / Checking: 4
(2 checks) Item #4 / Checking: 2
See attached file example.
How can I get the 2-sequence numbers? for the checks that does not have numbers, it could be filled out with a zero or negative number. Remember, no coding, only math code, see example below:
For the first value: QtyItems*QtyChecking/2
For the second value: QtyItems*QtyChecking/2 + 1
Thank you.

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