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

A141506

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

Terms

    a(0) =1a(1) =2a(2) =1a(3) =5a(4) =3a(5) =25a(6) =13a(7) =205a(8) =99a(9) =2849a(10) =1247a(11) =66677a(12) =26615a(13) =2633485a(14) =954340a(15) =175143651a(16) =57733315a(17) =19638725775a(18) =5882854746

External references