Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
A211816
Number of (n+1)X(n+1) -10..10 symmetric matrices with every 2X2 subblock having sum zero and two or three distinct values.
Terms
- a(0) =220a(1) =602a(2) =1368a(3) =2942a(4) =6088a(5) =12442a(6) =24924a(7) =50194a(8) =99390a(9) =199570a(10) =394162a(11) =793028a(12) =1569220a(13) =3170790a(14) =6300354a(15) =12799142a(16) =25565534a(17) =52235044a(18) =104925530a(19) =215604840a(20) =435513812a(21) =899750556a(22) =1827061522a(23) =3793414420a(24) =7740115362a(25) =16142443314
External references
- oeis: A211816