Number of n X n binary arrays, symmetric about the diagonal and under 90-degree rotation, with every 1 adjacent to at least one other 1, but at most one 1 adjacent horizontally and at most one 1 adjacent vertically.
A144057
Number of n X n binary arrays, symmetric about the diagonal and under 90-degree rotation, with every 1 adjacent to at least one other 1, but at most one 1 adjacent horizontally and at most one 1 adjacent vertically.
Terms
- a(0) =1a(1) =2a(2) =1a(3) =3a(4) =5a(5) =13a(6) =23a(7) =83a(8) =158a(9) =743a(10) =1983a(11) =10973a(12) =39092a(13) =269179a(14) =1193276a(15) =10361962a(16) =58314051a(17) =622131402a(18) =4633595266a(19) =60891994633a(20) =582192966557
External references
- oeis: A144057