Number of (n+1)X(n+1) -5..5 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
A211333
Number of (n+1)X(n+1) -5..5 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
Terms
- a(0) =61a(1) =153a(2) =359a(3) =811a(4) =1825a(5) =4073a(6) =9117a(7) =20435a(8) =46019a(9) =104103a(10) =236721a(11) =541185a(12) =1243505a(13) =2872291a(14) =6664963a(15) =15538035a(16) =36366709a(17) =85451073a(18) =201438293a(19) =476368999a(20) =1129466571a(21) =2684618219a(22) =6394000481a(23) =15257754137a(24) =36465654269a(25) =87277538267
External references
- oeis: A211333