Claude. To be fair, it had trouble OCR-ing it. After way too much back and forth about the pattern, it produced this:
=LET(
rows, SEQUENCE(INT((667-30)/13+1),1,30,13),
SUM(INDEX(AA:AA,rows))
)
Which is correct, but obviously the calculations would be best served by reorganizing the table and probably using a pivot table or at least grouping and subtotaling.
This is exactly what keeps me from switching. I don’t have the time or pull to do knuckle down on an important PC. Maybe when I have a backup one, I’ll do it. Who knows.