A000669 - cp's OEIS frontend

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.

n	a(n)
1	1
2	1
3	2
4	5
5	12
6	33
7	90
8	261
9	766
10	2312
11	7068
12	21965
13	68954
14	218751
15	699534
16	2253676
17	7305788
18	23816743
19	78023602
20	256738751
21	848152864
22	2811996972
23	9353366564
24	31204088381
25	104384620070
26	350064856815
27	1176693361956
28	3963752002320

[1, 1, 2, 5, 12, 33, 90, 261, 766, 2312, 7068, 21965, 68954, 218751, 699534, 2253676, 7305788, 23816743, 78023602, 256738751, 848152864, 2811996972, 9353366564, 31204088381, 104384620070, 350064856815, 1176693361956, 3963752002320]

cp's OEIS Frontend

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.

Table of values

List of values