Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
A211817
Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and one, two or three distinct values.
Terms
- a(0) =221a(1) =623a(2) =1477a(3) =3361a(4) =7389a(5) =16191a(6) =34993a(7) =76417a(8) =165745a(9) =365037a(10) =801507a(11) =1788695a(12) =3988703a(13) =9030407a(14) =20455109a(15) =46942737a(16) =107843925a(17) =250411345a(18) =582132123a(19) =1364670701a(20) =3202526531a(21) =7563851273a(22) =17879861115a(23) =42470025643a(24) =100944212731
External references
- oeis: A211817