Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and two, three or four distinct values.
A211820
Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and two, three or four distinct values.
Terms
- a(0) =220a(1) =2310a(2) =24280a(3) =255510a(4) =2692030a(5) =28396180a(6) =299874470a(7) =3170351150a(8) =33554420380a(9) =355508955450
External references
- oeis: A211820