A354850 a(n) is the number of free polyominoes of width 4 and size n.

1, 3, 21, 59, 198, 703, 2568, 8421, 26165, 78074, 229881, 668082, 1928220, 5523946, 15745682, 44666804, 126251748, 355692380, 999498933, 2802212026, 7841587533, 21907928927, 61123152811, 170333279738, 474197771123, 1319004492132, 3666181193067, 10183729521212

Offset: 4

Author

John Mason, Jun 08 2022

Keywords

• nonn

Comments

The sequence can be generated using a series of recursive formulas in a fashion similar to A352720 and A353067. These require respectively around 500 and 62000 formula lines, whereas a(n) requires about 10 million lines.

Links

• John Mason, Table of n, a(n) for n = 4..100
• John Mason, Java programs for calculating sequence, valid also for widths 2 and 3

Crossrefs

Cf. A000105, A352720, A353067.