Number of symmetric binary n X n matrices with every 1 adjacent horizontally (and vertically) to some 0.

A140196

Number of symmetric binary n X n matrices with every 1 adjacent horizontally (and vertically) to some 0.

Terms

    a(0) =1a(1) =5a(2) =21a(3) =175a(4) =2665a(5) =69147a(6) =3183841a(7) =259010439a(8) =36989095651

External references