Below is a possible solution to the problem Challenge 67 - Generate a Particular Sequence -

This consists of 2 logic.

  1. Generate Triangular number. The formula for which is n*(n+1)/2
  2. Generate Column Labels (A, B, AA, ZZ....) from numbers, the formula for which is

=SUBSTITUTE(ADDRESS(1,3,4),1,"") where 3 is for column C. So, we need to vary this 3.

The combined formula would be -