A063894 - cp's OEIS frontend

A063894 Start with x, y; then concatenate each word in turn with all preceding words, getting x y xy xxy yxy xxxy yxxy xyxxy ...; sequence gives number of words of length n. Also binary trees by degree: x y (x,y) (x,(x,y)) (y,(x,y)) (x,(x,(x,y))) (y,(x,(x,y))) ((x,y),(x,(x,y)))...

n	a(n)
1	2
2	1
3	2
4	4
5	10
6	25
7	68
8	187
9	532
10	1532
11	4492
12	13308
13	39870
14	120433
15	366656
16	1123504
17	3463050
18	10729234
19	33396202
20	104381385
21	327477814
22	1030903514
23	3255394686
24	10309154738
25	32732315724
26	104177891232
27	332308237666
28	1062192108053

[2, 1, 2, 4, 10, 25, 68, 187, 532, 1532, 4492, 13308, 39870, 120433, 366656, 1123504, 3463050, 10729234, 33396202, 104381385, 327477814, 1030903514, 3255394686, 10309154738, 32732315724, 104177891232, 332308237666, 1062192108053]

cp's OEIS Frontend

A063894 Start with x, y; then concatenate each word in turn with all preceding words, getting x y xy xxy yxy xxxy yxxy xyxxy ...; sequence gives number of words of length n. Also binary trees by degree: x y (x,y) (x,(x,y)) (y,(x,y)) (x,(x,(x,y))) (y,(x,(x,y))) ((x,y),(x,(x,y)))...

Table of values

List of values