A351615 Number of free polyominoes with n squares, having 180-degree rotational symmetry about the center of a square, and no other symmetry.

0, 0, 0, 0, 1, 0, 4, 0, 19, 1, 73, 4, 283, 25, 1090, 106, 4183, 463, 16105, 1892, 62170, 7752, 240907, 31212, 936447, 125609, 3651618, 503165, 14277519, 2014826, 55961118, 8058790, 219813564, 32231897, 865091976, 128897247, 3410498446, 515554767, 13466262587, 2062445063, 53245595410, 8252868076, 210800433323

Offset

1,7

Comments

The sequence enumerates a subset of the polyominoes enumerated by A006747.

Links

John Mason, Table of n, a(n) for n = 1..50

Example

a(5)=1 because of:
   OO
   O
  OO

Crossrefs

Cf. A006747, A234008, A351616.

Sequence in context: A156457 A058348 A184946 * A362058 A085618 A263626

Adjacent sequences: A351612 A351613 A351614 * A351616 A351617 A351618

Keyword

nonn

Author

John Mason, Feb 15 2022

Extensions

More terms from John Mason, Apr 15 2023

Status

approved