This should do what you are looking for. The formula creates the result in cell F4. In F16 is a simple LAMBDA and BYCOL.

=IFNA(DROP(REDUCE("",SEQUENCE(,10),
LAMBDA(u,v,VSTACK(u,HSTACK(SEQUENCE(,v,0,0),DROP(SEQUENCE(,11),,-v))))),1,1),0)

Both formulas can be combined to only display the final result.

=LET(_rows,IFNA(DROP(REDUCE("",SEQUENCE(,10),
LAMBDA(u,v,VSTACK(u,HSTACK(SEQUENCE(,v,0,0),DROP(SEQUENCE(,11),,-v))))),1,1),0),
BYROW(_rows,LAMBDA(c,SUM(c))))