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A216583 Number of unit-conjoined polydominoes of order n. 9
1, 1, 3, 20, 171, 1733, 18962, 215522, 2507188, 29635101 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,3
COMMENTS
A unit-conjoined polydomino is formed from n 1 X 2 non-overlapping rectangles (or dominoes) such that each pair of touching rectangles shares an edge of length 1. The internal arrangement of dominoes is not significant: figures are counted as distinct only if the shapes of their perimeters are different.
Figures that differ only by a rotation and/or reflection are regarded as equivalent (cf. A216595).
This sequence is A216492 without the condition that the adjacency graph of the dominoes forms a tree.
This is a subset of polydominoes. It appears that A216492(n) < a(n) < A056785(n) < A056786(n) < A210996(n) < A210988(n) < A210986(n), if n >= 3. - Omar E. Pol, Sep 17 2012
LINKS
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
CROSSREFS
Sequence in context: A051643 A213377 A357094 * A354018 A154644 A321276
KEYWORD
nonn,more,hard
AUTHOR
N. J. A. Sloane, Sep 09 2012
EXTENSIONS
a(4)-a(6) added by César Eliud Lozada, Sep 09 2012
a(7)-a(9) and name edited by Aaron N. Siegel, May 18 2022
STATUS
approved

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Last modified May 21 05:34 EDT 2024. Contains 372728 sequences. (Running on oeis4.)