Thank you all for your answers,

I've used this:

=LET(first,'Series Data'!Q$2:Q$21,
mul,108,
cella,BYROW(SEQUENCE(mul,1,0,20),LAMBDA(x,AVERAGE(OFFSET(first,INDEX(x,1,1),0)))),
cellb,BYROW(SEQUENCE(mul,1,0,20),LAMBDA(x,STDEV(OFFSET(first,INDEX(x,1,1),0)))),
DROP(TOCOL(HSTACK(TOCOL(TEXTSPLIT(REPT("|",mul),"|")),cella,cellb,TOCOL(TEXTSPLIT(REPT("|",mul),"|")))),-4))

Because 2161 is the maximum amount of data sets of 20, 108 is sufficient to harbor all possibilities. It gives the data how I requested, dropping down the avg, then stdev, then two blank rows.

Works like a charm, thanks again!!