A135017 - cp's OEIS frontend

A135017 a(n) is number of strings of length n that can be obtained by starting with abc and repeatedly doubling any substring in place and then discarding any string that contains two successive equal letters.

n	a(n)
1	0
2	0
3	1
4	0
5	2
6	1
7	3
8	5
9	7
10	15
11	20
12	48
13	60
14	156
15	205
16	489
17	761
18	1572
19	2796
20	5357
21	10174
22	19021
23	37272
24	69375
25	137759
26	258444
27	513696
28	976890
29	1934900
30	3727164
31	7358675
32	14316861
33	28217028
34	55288907
35	108942267
36	214462953
37	422973649
38	835145308
39	1649638479
40	3263689911
41	6457465848
42	12795025182
43	25355766038
44	50304700910

[0, 0, 1, 0, 2, 1, 3, 5, 7, 15, 20, 48, 60, 156, 205, 489, 761, 1572, 2796, 5357, 10174, 19021, 37272, 69375, 137759, 258444, 513696, 976890, 1934900, 3727164, 7358675, 14316861, 28217028, 55288907, 108942267, 214462953, 422973649, 835145308, 1649638479, 3263689911, 6457465848, 12795025182, 25355766038, 50304700910]

cp's OEIS Frontend

A135017 a(n) is number of strings of length n that can be obtained by starting with abc and repeatedly doubling any substring in place and then discarding any string that contains two successive equal letters.

Table of values

List of values