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.

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.

Terms

    a(0) =1a(1) =2a(2) =1a(3) =3a(4) =2a(5) =9a(6) =3a(7) =28a(8) =9a(9) =137a(10) =28a(11) =811a(12) =137a(13) =6884a(14) =811a(15) =75303a(16) =6884a(17) =1133287a(18) =75303a(19) =22573092a(20) =1133287a(21) =608722751a(22) =22573092a(23) =21933950111a(24) =608722751a(26) =21933950111

External references