Often we wish to incorporate into our formula a construction which, as that formula is copied down to successive rows, will generate a series of consecutive integers, usually beginning with 1.

A classic example is the standard INDEX/SMALL set-up for returning multiple values corresponding to a certain set of criteria, e.g.:

=INDEX($B1:$B10,SMALL(IF($A$1:$A$10="A",ROW($A$1:$A$10)-MIN(ROW($A$1:$A$10))+1),1))