Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.

A145778

Number of n X n binary arrays symmetric about the diagonal and under 90-degree rotation with all ones connected only either two adjacent vertically or two adjacent horizontally.

Terms

    a(0) =1a(1) =1a(2) =1a(3) =2a(4) =2a(5) =3a(6) =6a(7) =10a(8) =21a(9) =46a(10) =106a(11) =253a(12) =820a(13) =2128a(14) =8527a(15) =25843a(16) =122734a(17) =425169a(18) =2572337a(19) =9924088a(20) =75407076a(21) =331598798a(22) =3087553649a(23) =15467749658a(24) =179756366268

External references