A007727 - cp's OEIS frontend

A007727 Number of 2n-bead black-white strings with n black beads and fundamental period 2n.

n	a(n)
0	1
1	2
2	4
3	18
4	64
5	250
6	900
7	3430
8	12800
9	48600
10	184500
11	705430
12	2703168
13	10400598
14	40113164
15	155117250
16	601067520
17	2333606218
18	9075085776
19	35345263798
20	137846344000
21	538257870990
22	2104098258284
23	8233430727598
24	32247600966144

[1, 2, 4, 18, 64, 250, 900, 3430, 12800, 48600, 184500, 705430, 2703168, 10400598, 40113164, 155117250, 601067520, 2333606218, 9075085776, 35345263798, 137846344000, 538257870990, 2104098258284, 8233430727598, 32247600966144]

cp's OEIS Frontend

A007727 Number of 2n-bead black-white strings with n black beads and fundamental period 2n.

Table of values

List of values