You could use 6 one row portals....
The data in the columns is variable sometimes there might 2 records, sometimes it be might be 10 records.
If of course your records have consecutive ID's as per your example:
one portal would filter using:
Mod ( YourRecordID ; 2 ) = 0 gives evens
the other portal filters using:
Mod ( YourRecordID ; 2 ) <> 0 gives odds
Note the assumptions in symbister's post. What determines which record will be record 1 and which will be record 2 in your portal? We can guess that there is some logic to wanting the pattern you want and if we can identify that logic, there may be other ways to filter the portals to produce the results that you want.