Math Is Fun Forum

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 below the 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.

#. 
Item    Check #1       Check #2      Check #3         Check #4       Check #5          Check #6
I001    1 and 2          3 and 4         5 and 6         (0 or <0)        (0 or <0)            (0 or <0)
I002    7 and 8          (0 or <0)       (0 or <0)       (0 or <0)       (0 or <0)          (0 or <0)
I003    9 and 10         11 and 12     13 and 14       15 and 16     (0 or <0).          (0 or <0)
I004    17 and 18       19 and 20      (0 or <0)        (0 or <0)      (0 or <0)             (0 or <0)