500525

Appears in sequences

• Number of 5 X n 0..1 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.at n=16A281209
• a(n) is the number of canonical polygons with n edges having exactly 1 line of reflection symmetry.at n=22A307455