A161221 - cp's OEIS frontend

A161221 Consider necklaces with n beads, each black or white, where the n segments of cord between the beads are each colored red or green; a(n) is the number of different necklaces under the action of the dihedral group D_{2n}.

n	a(n)
0	1
1	4
2	9
3	20
4	51
5	136
6	414
7	1300
8	4371
9	15084
10	53508
11	192700
12	703346
13	2589304
14	9603954
15	35824240
16	134285331
17	505421344
18	1909144014
19	7234153420
20	27488865564
21	104717491064
22	399826699734
23	1529763696820
24	5864079144466
25	22518031691368
26	86607753541164

[1, 4, 9, 20, 51, 136, 414, 1300, 4371, 15084, 53508, 192700, 703346, 2589304, 9603954, 35824240, 134285331, 505421344, 1909144014, 7234153420, 27488865564, 104717491064, 399826699734, 1529763696820, 5864079144466, 22518031691368, 86607753541164]

cp's OEIS Frontend

A161221 Consider necklaces with n beads, each black or white, where the n segments of cord between the beads are each colored red or green; a(n) is the number of different necklaces under the action of the dihedral group D_{2n}.

Table of values

List of values