a(n) is the number of n-celled fixed polyominoes with at least 180 degree rotational symmetry about the center of a square in the lattice.

A390653

a(n) is the number of n-celled fixed polyominoes with at least 180 degree rotational symmetry about the center of a square in the lattice.

Terms

    a(0) =1a(1) =0a(2) =2a(3) =0a(4) =7a(5) =0a(6) =24a(7) =1a(8) =86a(9) =6a(10) =316a(11) =27a(12) =1178a(13) =114a(14) =4442a(15) =472a(16) =16896a(17) =1926a(18) =64716a(19) =7789a(20) =249283a(21) =31348a(22) =964708a(23) =125802a(24) =3748031a(25) =503948a(26) =14610484a(27) =2016677a(28) =57118440a(29) =8065830

External references