a(n) is the number of 2n-celled fixed polyominoes with at least 180 degree rotational symmetry about the midpoint of a horizontal edge of a square in the lattice.
A390654
a(n) is the number of 2n-celled fixed polyominoes with at least 180 degree rotational symmetry about the midpoint of a horizontal edge of a square in the lattice.
Terms
- a(0) =1a(1) =3a(2) =10a(3) =35a(4) =127a(5) =472a(6) =1778a(7) =6760a(8) =25896a(9) =99783a(10) =386320a(11) =1501661a(12) =5856748a(13) =22908230a(14) =89828072a(15) =353006402a(16) =1389925354a(17) =5482090062a(18) =21655518914a(19) =85662816994a(20) =339281765621
External references
- oeis: A390654