Half the number of (n+1)X(n+1) symmetric 0..1 arrays with no 2X2 subblock summing to 2.
A213690
Half the number of (n+1)X(n+1) symmetric 0..1 arrays with no 2X2 subblock summing to 2.
Terms
- a(0) =3a(1) =13a(2) =70a(3) =529a(4) =5148a(5) =68798a(6) =1220409a(7) =29377751a(8) =949700962a(9) =41536397680
External references
- oeis: A213690