A216595 Number of distinct connected planar figures that can be formed from 1 X 2 rectangles (or dominoes) such that each pair of touching rectangles shares exactly one edge, of length 1.

1, 2, 14, 126, 1267, 13550, 150665

Offset: 0

Author

N. J. A. Sloane, Sep 08 2012

Keywords

• nonn
• more

Comments

Figures that differ by a rotation or reflection are regarded as distinct (cf. A216583).

This sequence is A216581 without the condition that the adjacency graph of the dominoes forms a tree.

An example: The two solutions

V H -

| V

H - |

and

H - V

V |

| H -

are considered to be the same because the resulting shape is the same.

Links

• César E. Lozada, Illustration of terms n <= 4 of A216583
• Manfred Scheucher, Python Script
• N. J. A. Sloane, Illustration of initial terms of A056786, A216598, A216583, A216595, A216492, A216581 (Exclude figures marked (A))
• N. J. A. Sloane, Illustration of third term of A056786, A216598, A216583, A216595, A216492, A216581 (a better drawing for the third term)
• M. Vicher, Polyforms
• Index entries for sequences related to dominoes

Crossrefs

Cf. A056786, A216598, A216583, A216595, A216492, A216581.

Extensions

Terms a(4)-a(6) added by César Eliud Lozada, Sep 09 2012