Number of (n+1)X(n+1) -8..8 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.

A211467

Number of (n+1)X(n+1) -8..8 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.

Terms

    a(0) =120a(1) =260a(2) =508a(3) =940a(4) =1734a(5) =3126a(6) =5690a(7) =10276a(8) =18758a(9) =34230a(10) =63068a(11) =116594a(12) =217310a(13) =407026a(14) =767450a(15) =1454628a(16) =2771646a(17) =5306940a(18) =10202586a(19) =19697838a(20) =38146332a(21) =74135060a(22) =144403432a(23) =282088738a(24) =551970304a(25) =1082582606a(26) =2125859552a(27) =4182450010

External references