A001683 - cp's OEIS frontend

A001683 Number of one-sided triangulations of the disk; or flexagons of order n; or unlabeled plane trivalent trees (n-2 internal vertices, all of degree 3 and hence n leaves).

n	a(n)
2	1
3	1
4	1
5	1
6	4
7	6
8	19
9	49
10	150
11	442
12	1424
13	4522
14	14924
15	49536
16	167367
17	570285
18	1965058
19	6823410
20	23884366
21	84155478
22	298377508
23	1063750740
24	3811803164
25	13722384546
26	49611801980
27	180072089896
28	655977266884
29	2397708652276
30	8791599732140
31	32330394085528

[1, 1, 1, 1, 4, 6, 19, 49, 150, 442, 1424, 4522, 14924, 49536, 167367, 570285, 1965058, 6823410, 23884366, 84155478, 298377508, 1063750740, 3811803164, 13722384546, 49611801980, 180072089896, 655977266884, 2397708652276, 8791599732140, 32330394085528]

cp's OEIS Frontend

A001683 Number of one-sided triangulations of the disk; or flexagons of order n; or unlabeled plane trivalent trees (n-2 internal vertices, all of degree 3 and hence n leaves).

Table of values

List of values