Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.
A211814
Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and three distinct values.
Terms
- a(0) =188a(1) =414a(2) =812a(3) =1510a(4) =2778a(5) =5014a(6) =9064a(7) =16350a(8) =29566a(9) =53808a(10) =98098a(11) =180732a(12) =333300a(13) =622046a(14) =1161392a(15) =2193998a(16) =4144530a(17) =7912796a(18) =15101998a(19) =29086670a(20) =55991176a(21) =108595704a(22) =210489002a(23) =410470320a(24) =799923628a(25) =1566429434a(26) =3065502158
External references
- oeis: A211814