A387003 Triangle read by rows: T(n,d) is the number of free (d,2)-polyominoids of size n, 2 <= d <= n+1.

1, 1, 2, 2, 9, 12, 5, 54, 95, 103

Offset: 1

Author

Pontus von Brömssen, Aug 14 2025

Keywords

• nonn
• tabl
• more

Comments

If d > n+1, there are T(n,n+1) such polyominoids. The triangle only includes the values for d <= n+1.

Examples

			Triangle begins:
  n\d| 2  3  4   5
  ---+------------
  1  | 1
  2  | 1  2
  3  | 2  9 12
  4  | 5 54 95 103
		

Links

• Wikipedia, Polyominoid.
• Index entries for sequences related to polyominoes.

Crossrefs

Columns: A000105 (d=2), A075679 (d=3), A366334 (d=4).

Cf. A330891 (polyominoes), A385583 (polysticks), A385715 (fixed), A387002, A387004, A387005 (main diagonal).

Formula

T(n,d) = Sum_{k=1..d} A387004(n,k).