Running the Numbers on Babette

Each square has four sides.  The number of double-crochets in each row is 4n-1.  So a two row square has 

    4 * [ (4*1) - 1 + (4*2) - 1 ] = 40.  

A four row square has 

    40 + 4 * [ (4*3) - 1 + (4*4) - 1 ] = 144.

Etc.

I'm using sport weight yarn instead of the called-for fingering weight and I'm using a size F needle instead of the called-for E.  The largest square I've completed is a ten row.  It weighs 45 g.  I've worked out the following table:

I don't have 24 balls of yarn so I'm contemplating my options.  The pattern conveniently groups the motifs into ten groups that spiral out from a center 12-row square in a log-cabin fashion.  So, I could probably do nine groups and end up with a good sized blanket.  Or would it be better to scale back the project to a pillowcase and repurpose the unused yarn for something else?  (And use the money I save to pay for Pixelmator, so I don't have a watermark on my table!)