A141486 - OEIS

A141486

Number of n X n binary matrices, symmetric about the diagonal and under 90-degree rotation, with no more than 1 one in any 2 X 2 subblock.

1, 2, 1, 3, 2, 9, 3, 28, 9, 137, 28, 811, 137, 6884, 811, 75303, 6884, 1133287, 75303, 22573092, 1133287, 608722751, 22573092, 21933950111, 608722751, 1064082678978, 21933950111, 69200610896639, 1064082678978, 6047740350081131, 69200610896639