A083563 - cp's OEIS frontend

A083563 Number of binary rooted trees (every node has out-degree 0 or 2) with n labeled leaves (2n-1 nodes in all) and at most 2 distinct labels. Also the number of expressions in at most two variables constructible with n-1 instances of a single commutative and nonassociative binary operator.

n	a(n)
0	0
1	2
2	3
3	6
4	18
5	54
6	183
7	636
8	2316
9	8610
10	32763
11	126582
12	495981
13	1964718
14	7857939
15	31682202
16	128644290
17	525573252
18	2158930398
19	8911295286
20	36942107373
21	153742174722
22	642088530453
23	2690224616904
24	11304554951127
25	47630390054802
26	201181338802308
27	851690762495448

[0, 2, 3, 6, 18, 54, 183, 636, 2316, 8610, 32763, 126582, 495981, 1964718, 7857939, 31682202, 128644290, 525573252, 2158930398, 8911295286, 36942107373, 153742174722, 642088530453, 2690224616904, 11304554951127, 47630390054802, 201181338802308, 851690762495448]

cp's OEIS Frontend

A083563 Number of binary rooted trees (every node has out-degree 0 or 2) with n labeled leaves (2n-1 nodes in all) and at most 2 distinct labels. Also the number of expressions in at most two variables constructible with n-1 instances of a single commutative and nonassociative binary operator.

Table of values

List of values