A259090 Number of symmetrical n-celled polyominoes.

1, 1, 2, 4, 7, 15, 24, 53, 89, 194, 323, 722, 1197, 2706, 4465, 10229, 16814, 38900, 63721, 148808, 243006, 571937, 931305, 2207561, 3584959, 8551309, 13851410, 33229843, 53694326, 129485500, 208738348, 505796115, 813532119, 1980023840, 3177764415

Offset: 1

Author

N. J. A. Sloane, Jun 18 2015

Keywords

• nonn

Links

• John Mason, Table of n, a(n) for n = 1..50 (This version corrects erroneous values from a(44) onwards in previous version)
• T. R. Parkin, L. J. Lander, and D. R. Parkin, Polyomino Enumeration Results, presented at SIAM Fall Meeting, 1967, and accompanying letter from T. J. Lander (annotated scanned copy). See page 21. The 15th entry is not included because their value for A000105(15) was incorrect.

Crossrefs

Cf. A000105, A006749.

Programs

Mathematica

A000105 = Cases[Import["https://oeis.org/A000105/b000105.txt", "Table"], {, }][[All, 2]];
A006749 = Cases[Import["https://oeis.org/A006749/b006749.txt", "Table"], {, }][[All, 2]];
a[n_] := A000105[[n + 1]] - A006749[[n]];
Array[a, 28] (* Jean-François Alcover, Aug 27 2019 *)

Formula

a(n) = A000105(n) - A006749(n).

Extensions

a(5)-a(6) corrected and a(15)-a(28) from Andrew Howroyd, Dec 04 2018

a(29) and beyond from John Mason, Dec 22 2021