cp's OEIS Frontend

A216583 Number of unit-conjoined polydominoes of order n.

%I A216583 #50 May 22 2022 02:17:55
%S A216583 1,1,3,20,171,1733,18962,215522,2507188,29635101
%N A216583 Number of unit-conjoined polydominoes of order n.
%C A216583 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.
%C A216583 Figures that differ only by a rotation and/or reflection are regarded as equivalent (cf. A216595).
%C A216583 This sequence is A216492 without the condition that the adjacency graph of the dominoes forms a tree.
%C A216583 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
%H A216583 César E. Lozada, <a href="/A216583/a216583.pdf">Illustration of terms n <= 4 of A216583</a>
%H A216583 N. J. A. Sloane, <a href="/A056786/a056786.jpg">Illustration of initial terms of A056786, A216598, A216583, A216595, A216492, A216581</a> (Exclude figures marked (A))
%H A216583 N. J. A. Sloane, <a href="/A056786/a056786.pdf">Illustration of third term of A056786, A216598, A216583, A216595, A216492, A216581</a> (a better drawing for the third term)
%H A216583 M. Vicher, <a href="http://www.vicher.cz/puzzle/polyforms.htm">Polyforms</a>
%H A216583 <a href="/index/Do#domino">Index entries for sequences related to dominoes</a>
%Y A216583 Cf. A056786, A216598, A216583, A216595, A216492, A216581.
%K A216583 nonn,more,hard
%O A216583 0,3
%A A216583 _N. J. A. Sloane_, Sep 09 2012
%E A216583 a(4)-a(6) added by _César Eliud Lozada_, Sep 09 2012
%E A216583 a(7)-a(9) and name edited by _Aaron N. Siegel_, May 18 2022