Free polyominoes with 2n squares, having 180-degree rotational symmetry about a square mid-side.
A234010
Free polyominoes with 2n squares, having 180-degree rotational symmetry about a square mid-side.
Terms
- a(0) =1a(1) =2a(2) =6a(3) =19a(4) =67a(5) =241a(6) =901a(7) =3398a(8) =12991a(9) =49958a(10) =193317a(11) =751080a(12) =2928956a(13) =11455059a(14) =44916219a(15) =176506797a(16) =694970938a(17) =2741058805a(18) =10827790934a(19) =42831461499a(20) =169641003412a(21) =672657627655
External references
- oeis: A234010