Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
A146050
Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 2X2 block with tail 1,1 1,2 1,3 2,2 2,3 in any orientation.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =3a(6) =9a(7) =19a(8) =37a(9) =115a(10) =481a(11) =2395a(12) =10969a(13) =57003a(14) =371055a(15) =2992969a(16) =26653005a(17) =266091447a(18) =3019768963a(19) =42043911685a(20) =666291390951
External references
- oeis: A146050