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A006762 Number of strictly 2-dimensional fixed polyominoes with n cells.
(Formerly M3534)
6

%I M3534 #26 Sep 06 2019 10:52:28

%S 0,0,4,17,61,214,758,2723,9908,36444,135266,505859,1903888,7204872,

%T 27394664,104592935,400795842,1540820540,5940738674,22964779658,

%U 88983512781,345532572676,1344372335522,5239988770266,20457802016009,79992676367106,313224032098242,1228088671826971

%N Number of strictly 2-dimensional fixed polyominoes with n cells.

%C This sequence counts only polyominoes that are strictly 2-dimensional - it excludes those where all the squares are in a single line. Thus for n > 1, a(n) = A001168(n) - 2. - _Franklin T. Adams-Watters_, Jul 29 2007

%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

%H Jean-François Alcover, <a href="/A006762/b006762.txt">Table of n, a(n) for n = 1..56</a>

%H W. F. Lunnon, <a href="https://doi.org/10.1093/comjnl/18.4.366">Counting multidimensional polyominoes</a>, Computer Journal 18 (1975), no. 4, pp. 366-367.

%F a(n) = A001168(n) - 2 for n > 1. - _Franklin T. Adams-Watters_, Jul 29 2007

%t A001168 = Cases[Import["https://oeis.org/A001168/b001168.txt", "Table"], {_, _}][[All, 2]];

%t a[n_] := If[n == 1, 0, A001168[[n]] - 2];

%t Array[a, 56] (* _Jean-François Alcover_, Sep 06 2019 *)

%Y A column of A195739.

%Y Cf. A001168.

%K nonn

%O 1,3

%A _N. J. A. Sloane_

%E Name clarified and a(18)-a(28) from _Andrew Howroyd_, Dec 04 2018

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Last modified March 28 08:22 EDT 2024. Contains 371236 sequences. (Running on oeis4.)