Number of (n+1)X(n+1) -6..6 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
A211257
Number of (n+1)X(n+1) -6..6 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
Terms
- a(0) =85a(1) =231a(2) =547a(3) =1283a(4) =2901a(5) =6595a(6) =14775a(7) =33409a(8) =75157a(9) =170723a(10) =387687a(11) =888293a(12) =2039449a(13) =4718583a(14) =10949039a(15) =25566565a(16) =59877913a(17) =140930679a(18) =332585711a(19) =787830185a(20) =1870341077a(21) =4452666039a(22) =10618825855a(23) =25375634725a(24) =60720707925
External references
- oeis: A211257