I agree, but I'm saying something stronger here. The reaction notation is equivalent to a FRACTRAN program. Given a prime<->species correspondence, it survive

I agree, but I'm saying something stronger here. The reaction notation is equivalent to a FRACTRAN program. Given a prime<->species correspondence, it survives a round trip to and from fractional notation, so to speak ("assembly" and "disassembly"). It's just another way of writing prime decompositions. Perfectly logical agents who can see the entirety of logical consequence would think "eh, what's the big deal? it's equivalent!" But, for whatever reason, the notation finally made me "get" FRACTRAN.