A121753 Number of deco polyominoes of height n in which all columns end at an odd level. A deco polyomino is a directed column-convex polyomino in which the height, measured along the diagonal, is attained only in the last column.

1, 1, 2, 6, 16, 62, 230, 1114, 5268, 30702, 176226, 1201638, 8107464, 63339702, 491010102, 4324845834, 37867131900, 371275954758, 3623124865986, 39137296073094, 421150512316032, 4969568447400366, 58455531552960198

Offset: 1

Author

Emeric Deutsch, Aug 23 2006

Keywords

• nonn

Comments

a(n)=A121698(n,0).

Examples

			a(2)=1 because the deco polyominoes of height 2 are the vertical and horizontal dominoes and only the horizontal one has all of its columns ending at an odd level.
		

References

• E. Barcucci, S. Brunetti and F. Del Ristoro, Succession rules and deco polyominoes, Theoret. Informatics Appl., 34, 2000, 1-14.
• E. Barcucci, A. Del Lungo and R. Pinzani, "Deco" polyominoes, permutations and random generation, Theoretical Computer Science, 159, 1996, 29-42.

Crossrefs

Cf. A121698, A121751.

Programs

Maple

a[1]:=1: a[2]:=1: for n from 3 to 26 do a[n]:= (1+2*floor((n-2)/2))*a[n-1]-(floor((n-1)/2)*floor((n-2)/2)-1)*a[n-2] od: seq(a[n],n=1..26);

Formula

Recurrence relation: a(n)=(1+2floor((n-2)/2))a(n-1)-[floor((n-1)/2)floor((n-2)/2)-1]a(n-2) for n>=3, a(1)=1, a(2)=1.