=SEQUENCE(rows, [columns], [start], [step]) returns a list or grid of numbers: SEQUENCE(5) is 1 to 5 down a column, SEQUENCE(1,12) is 1 to 12 across, SEQUENCE(4,1,100,25) is 100, 125, 150, 175.
To use a spilled result elsewhere, refer to its first cell followed by #: if H2 holds =UNIQUE(B2:B16), then H2# means "the whole list, however long it's today". =COUNTA(H2#) counts it, and =SUMIFS(F2:F16,B2:B16,H2#) spills a total next to every item.
Spill references are the reason dynamic-array reports don't need editing when the data grows.