62170

Appears in sequences

• Number of rotationally symmetric polyominoes with n cells (that is, polyominoes with exactly the symmetry group C_2 generated by a 180-degree rotation).at n=20A006747
• Expansion of x/((1-x)*(1-x^2-2*x^3)).at n=27A077882
• Number of free polyominoes with n squares, having 180-degree rotational symmetry about the center of a square, and no other symmetry.at n=20A351615