Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 5-point barb 1,1 1,2 2,2 2,3 3,2 in any orientation.
A146140
Number of n X n binary arrays symmetric about both diagonal and antidiagonal with all ones connected only in a 5-point barb 1,1 1,2 2,2 2,3 3,2 in any orientation.
Terms
- a(0) =1a(1) =1a(2) =1a(3) =1a(4) =1a(5) =1a(6) =5a(7) =13a(8) =25a(9) =57a(10) =197a(11) =913a(12) =4565a(13) =21033a(14) =117411a(15) =799889a(16) =6782571a(17) =62778947a(18) =652383615a(19) =7631737235a(20) =109519353841
External references
- oeis: A146140