Based on Dave's change, formula from
B2 onwards should read:
How it works
ROWS function divided by 3 says that for every 3 rows you fill down the formula, it will look one cell further down for A's value. The first
$B$2 uses absolute referencing because you always want the formula to remember where the first cell in B is. The second
$B2 will fill down and tell it how far to count to.
CEILING function with a precision of 1 will ensure your ROWS result (#) is rounded up to the nearest whole number, and so tells us how far down A to go.
The INDEX function uses your result to return the #'th item from your table in column A.