User blog comment:Primussupremus/Another attempt at defining some type of notation./@comment-31663462-20170419011223

I recommend starting with your (_,_,_) and stating all the rules on how to expand it. While there is a logical progression, I can't think exactly how you think, and unless you state the rules clearly, I can't use this. For example, why does  3(3,d,3)3 = 3,d,3 ? Its not clear here.