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

1,3

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.

Formula

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

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 *)

Crossrefs

Cf. A000105, A006749.

Sequence in context: A333613 A171276 A027167 * A358832 A232464 A264292

Adjacent sequences: A259087 A259088 A259089 * A259091 A259092 A259093

Keyword

nonn

Author

N. J. A. Sloane, Jun 18 2015

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

Status

approved