# In Excel, is there an array formula that returns a power series (like SERIESSUM, but returning an array of the series instead of its sum)?

I know I could construct a quick sheet to build the series across a range of cells, but I'd like to be able to get the power series from an array formula in a single cell. (I can then nest this within another function, for example.)

The `SERIESSUM` function works like this:

``````SERIESSUM(x,n,m,a) = a1x^n + a2x^(n+m) + a3x^(n+2m) + ... + ajx(n+(j-1)m)
``````

Where the input `a` is an array of coefficients, and `j` is the length of `a`.

The function I'm looking for would similarly return

``````[a1x^n, a2x^(n+m), a3x^(n+2m), ..., ajx(n+(j-1)m)]
``````

This could either be a function that I haven't found, or a full array formula that results in the same output.

Any help would be greatly appreciated, thanks.

• Easy to do with a VBA User Defined Function................any interest ?? – Gary's Student Feb 2 '20 at 14:24
• That's interesting, I didn't know User Defined Functions were an option - they look great. I'd like my sheet to work in both Excel and Google Sheets, but it looks like I could define the same custom function in Javascript for sheets to use. I'm still interested in a 'pure' function solution, but this is really useful to know about, thanks! – JRVeale Feb 2 '20 at 17:55