Simple transformation rules lead to complex and beautiful molecules

I'm messing around with some code for a new project. The code starts with the first molecule shown below (NCCN) and repeatedly applies two transformation: it inserts a C atom between 2 C atoms (CC>>CCC) and cyclizes 3 C atoms (CCC>>C1CC1). The image below shows the result for 7 cycles of this, i.e. cycle 1 creates NCCCN, cycle 2 creates  NC1CC1N and NCCCCN, etc.

After 7 cycles these two simples transformations lead to 121 molecules, some of which are quite beautiful in my opinion. I wonder how many of these have been made.

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