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

0,2

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

Table of n, a(n) for n=0..6.

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.

Sequence in context: A060468 A349261 A121082 * A155650 A331397 A363983

Adjacent sequences: A216592 A216593 A216594 * A216596 A216597 A216598

Keyword

nonn,more

Author

N. J. A. Sloane, Sep 08 2012

Extensions

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

Status

approved