A simple context-free grammar in a labeled universe: labeled version of A049140.
A052740
A simple context-free grammar in a labeled universe: labeled version of A049140.
Terms
- a(0) =0a(1) =1a(2) =2a(3) =12a(4) =144a(5) =2400a(6) =50400a(7) =1290240a(8) =39070080a(9) =1365154560a(10) =54047347200
External references
- oeis: A052740