I get a different answer from SERIESSUM when I use your formula.

=SERIESSUM(1.003,0,1,COUNT(--(ROW(1:8)0))) gives 8 when entered as an array
formula and 1 when entered as a regular formula.

=SERIESSUM(1.003,0,1,{1,1,1,1,1,1,1,1}) gives 8.084506.

I noticed that COUNT(--(ROW(1:8)0)) gives {1;1;1;1;1;1;1;1} whereas Excel's
arrays are typically {1,1,1,1,1,1,1,1}. In my experience, semicolons are
used to break for rows and commas are used when entering numbers across a
row.

Thanks,
RK

"Ron Coderre" wrote in message
...
Would this work for you?:

=COUNT(--(ROW(1:360)0))

Note: commit that array formula by pressing [Ctrl]+[Shift]+[Enter]

It seemed to work in your example formula:
=SERIESSUM(1.005,1,1,COUNT(--(ROW(1:360)0)))

Again: commit that array formula by pressing [Ctrl]+[Shift]+[Enter]

Regards,
Ron