Number of series-reduced planted trees with n leaves. Also the number of essentially series series-parallel networks with n edges; also the number of essentially parallel series-parallel networks with n edges.
A000669
Number of series-reduced planted trees with n leaves. Also the number of essentially series series-parallel networks with n edges; also the number of essentially parallel series-parallel networks with n edges.
Terms
- a(0) =1a(1) =1a(2) =2a(3) =5a(4) =12a(5) =33a(6) =90a(7) =261a(8) =766a(9) =2312a(10) =7068a(11) =21965a(12) =68954a(13) =218751a(14) =699534a(15) =2253676a(16) =7305788a(17) =23816743a(18) =78023602a(19) =256738751a(20) =848152864a(21) =2811996972a(22) =9353366564a(23) =31204088381a(24) =104384620070a(25) =350064856815
External references
- oeis: A000669