Number of (n+1)X(n+1) -11..11 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.
A211711
Number of (n+1)X(n+1) -11..11 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.
Terms
- a(0) =230a(1) =516a(2) =1030a(3) =1908a(4) =3528a(5) =6312a(6) =11390a(7) =20316a(8) =36520a(9) =65646a(10) =118702a(11) =216006a(12) =394802a(13) =728492a(14) =1348550a(15) =2522796a(16) =4730304a(17) =8960110a(18) =16997998a(19) =32539860a(20) =62348810a(21) =120381720a(22) =232534604a(23) =451979570a(24) =878630354a(25) =1716513328a(26) =3353186654
External references
- oeis: A211711