A351191 - cp's OEIS frontend

A351191 Number of polyominoes of 4n cells with both horizontal and vertical symmetries, for which the 180-degree rotational symmetry has an axis that coincides with a vertex of a square of the underlying matrix, but without 90-degree rotational symmetry.

n	a(n)
1	0
2	1
3	2
4	9
5	29
6	106
7	372
8	1356
9	4928
10	18200
11	67541
12	252847
13	951615
14	3602131
15	13696141
16	52295335
17	200393559
18	770406039
19	2970353199
20	11482373919
21	44491696182
22	172766226170
23	672185941552
24	2619994156474
25	10228900153083
26	39996337310835
27	156612012801698

[0, 1, 2, 9, 29, 106, 372, 1356, 4928, 18200, 67541, 252847, 951615, 3602131, 13696141, 52295335, 200393559, 770406039, 2970353199, 11482373919, 44491696182, 172766226170, 672185941552, 2619994156474, 10228900153083, 39996337310835, 156612012801698]

cp's OEIS Frontend

A351191 Number of polyominoes of 4n cells with both horizontal and vertical symmetries, for which the 180-degree rotational symmetry has an axis that coincides with a vertex of a square of the underlying matrix, but without 90-degree rotational symmetry.

Table of values

List of values