A260585 - cp's OEIS frontend

A260585 Number of ways to place 2n rooks on an n X n board, with 2 rooks in each row and each column, multiple rooks in a cell allowed, and exactly 2 rooks below the main diagonal.

n	a(n)
2	1
3	11
4	72
5	367
6	1630
7	6680
8	26082
9	98870
10	368045
11	1354850
12	4953503
13	18035279
14	65499031
15	237511321
16	860471110
17	3115667369
18	11277816388
19	40814611818
20	147692103728
21	534404499040
22	1933597628291
23	6996040095316
24	25312367524557
25	91581960107817
26	331348634005165

[1, 11, 72, 367, 1630, 6680, 26082, 98870, 368045, 1354850, 4953503, 18035279, 65499031, 237511321, 860471110, 3115667369, 11277816388, 40814611818, 147692103728, 534404499040, 1933597628291, 6996040095316, 25312367524557, 91581960107817, 331348634005165]

cp's OEIS Frontend

A260585 Number of ways to place 2n rooks on an n X n board, with 2 rooks in each row and each column, multiple rooks in a cell allowed, and exactly 2 rooks below the main diagonal.

Table of values

List of values