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

4,2

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.

Sequence in context: A356809 A162394 A129212 * A328042 A331082 A117984

Adjacent sequences: A354847 A354848 A354849 * A354851 A354852 A354853

Keyword

nonn

Author

John Mason, Jun 08 2022

Status

approved