a(n) is the number of 2n-celled fixed polyominoes with at least 180 degree rotational symmetry about a vertex of a square in the lattice.
A390655
a(n) is the number of 2n-celled fixed polyominoes with at least 180 degree rotational symmetry about a vertex of a square in the lattice.
Terms
- a(0) =0a(1) =1a(2) =4a(3) =14a(4) =50a(5) =186a(6) =704a(7) =2685a(8) =10312a(9) =39841a(10) =154642a(11) =602468a(12) =2354592a(13) =9227412a(14) =36246300a(15) =142671941a(16) =562600898a(17) =2222092230a(18) =8789217470a(19) =34809890792a(20) =138027690188a(21) =547891969992
External references
- oeis: A390655