Number of (n+1)X(n+1) -6..6 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.

A211256

Number of (n+1)X(n+1) -6..6 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.

Terms

    a(0) =84a(1) =218a(2) =482a(3) =1036a(4) =2134a(5) =4382a(6) =8810a(7) =17818a(8) =35538a(9) =71522a(10) =142458a(11) =286522a(12) =571602a(13) =1151174a(14) =2303198a(15) =4648814a(16) =9332754a(17) =18885906a(18) =38047946a(19) =77198226a(20) =156057706a(21) =317451158a(22) =643803786a(23) =1312796154a(24) =2670343286a(25) =5457409302a(26) =11131101682

External references