

A001168


Number of fixed polyominoes with n cells.
(Formerly M1639 N0641)


28



1, 2, 6, 19, 63, 216, 760, 2725, 9910, 36446, 135268, 505861, 1903890, 7204874, 27394666, 104592937, 400795844, 1540820542, 5940738676, 22964779660, 88983512783, 345532572678, 1344372335524, 5239988770268, 20457802016011, 79992676367108, 313224032098244, 1228088671826973
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

Number of rookwise connected patterns of n square cells.
N. Madras proved in 1999 the existence of the lim_{n \to \infty} a(n+1)/a(n), which is the real limit growth rate of the number of polyominoes; and hence, this limit is equal to lim_{n \to \infty} a(n)^{1/n}, the wellknown Klarner's constant. The currently bestknown lower and upper bounds on this constant are 3.9801 (Barequet et al., 2006) and 4.6496 (Klarner and Rivest, 1973), respectively. But see also Knuth (2014).


REFERENCES

G. Barequet, M. Moffie, A. Ribo, and G. Rote, Counting polyominoes on twisted cylinders, Integers (electronic journal, 6 (2006), A22, 37 pp.
Stirling Chow and Frank Ruskey, Gray codes for columnconvex polyominoes and a new class of distributive lattices, Discrete Mathematics, 309 (2009), 52845297. [From N. J. A. Sloane, Sep 15 2009]
A. R. Conway and A. J. Guttmann, On twodimensional percolation, J. Phys. A: Math. Gen. 28(1995) 891904.
S. R. Finch, Mathematical Constants, Cambridge, 2003, pp. 378382.
J. Fortier, A. Goupil, J. Lortie and J. Tremblay, Exhaustive generation of gominoes, Theoretical Computer Science, 2012; http://dx.doi.org/10.1016/j.tcs.2012.02.032.  From N. J. A. Sloane, Sep 20 2012
J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 229.
A. J. Guttmann, ed., Polygons, Polyominoes and Polycubes, Springer, 2009, p. 478. (Table 16.10 has 56 terms of this sequence.) [From Robert A. Russell, Nov 05 2010]
I. Jensen and A. J. Guttmann, Statistics of lattice animals (polyominoes) and polygons. J. Phys. A 33, L257L263 (2000).
D. A. Klarner and R. L. Rivest, A procedure for improving the upper bound for the number of nominoes, Canadian J. of Mathematics, 25 (1973), 585602.
C. Lesieur, L. Vuillon, From Tilings to Fibers  Biomathematical Aspects of Fold Plasticity, Chapter 13 (pages 395422) of "Oligomerization of Chemical and Biological Compounds" (?), 2014; http://dx.doi.org/10.5772/58577
W. F. Lunnon, Counting polyominoes, pp. 347372 of A. O. L. Atkin and B. J. Birch, editors, Computers in Number Theory. Academic Press, NY, 1971.
W. F. Lunnon, Counting hexagonal and triangular polyominoes, pp. 87100 of R. C. Read, editor, Graph Theory and Computing. Academic Press, NY, 1972.
N. Madras, A pattern theorem for lattice clusters, Annals of Combinatorics, 3 (1999), 357384.
D. H. Redelmeier, Counting polyominoes: yet another attack, Discrete Math., 36 (1981), 191203.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).


LINKS

I. Jensen, Table of n, a(n) for n = 1..56
S. R. Finch, Klarner's Lattice Animal Constant
I. Jensen, Enumerations of lattice animals and trees, arXiv:condmat/0007239.
I. Jensen, Home page
I. Jensen, More terms
D. E. Knuth, Program
D. E. Knuth, First 47 terms
D. E. Knuth, Problems That Philippe Would Have Loved, Paris 2014.
Tomas Oliveira e Silva, Enumeration of polyominoes
Eric Weisstein's World of Mathematics, Polyomino


FORMULA

For asymptotics, see Knuth (2014).


MATHEMATICA

(* This program is not convenient for more than 12 terms *) cyclic[p_] := Module[{i = p, ans = {p}}, While[(i = rot[i]) != p, AppendTo[ans, i]]; ans]; dihedral[p_] := Flatten[({#1, ref[#1]} & ) /@ cyclic[p], 1]; canonical[p_] := Union[(#1  (I*Min[Im[p]] + Min[Re[p]]) & ) /@ p]; allPieces[p_] := Union[canonical /@ dihedral[p]]; polyominoes[1] := {{0}}; polyominoes[n_] := polyominoes[n] = Module[{f, fig, ans = {}}, fig = ((f = #1; ({f, #1 + 1, f, #1 + I, f, #1  1, f, #1  I} & ) /@ f) & ) /@ polyominoes[n  1]; fig = Partition[Flatten[fig], n]; f = Select[Union[canonical /@ fig], Length[#1] == n & ]; While[f != {}, ans = {ans, First[f]}; f = Complement[f, allPieces[First[f]]]]; Partition[Flatten[ans], n]]; a[n_] := a[n] = Length[polyominoes[n]]; Table[Print[{n, a[n]}]; a[n], {n, 1, 12}] (* JeanFrançois Alcover, Jan 15 2013, copied from Jaime RangelMondragón's article *)


CROSSREFS

Cf. A000105, A006746, A056877, A006748, A056878, A006747, A006749, A006884, A006885, A006877, A006878, A033492.
A006762 is another version.
Sequence in context: A057409 A141771 A001170 * A193111 A119255 A071969
Adjacent sequences: A001165 A001166 A001167 * A001169 A001170 A001171


KEYWORD

nonn,nice


AUTHOR

N. J. A. Sloane.


EXTENSIONS

Extended to n=28 by Tomas Oliveira e Silva. Extended to n=46 by Iwan Jensen. Verified (and one more term found) by D. E. Knuth, Jan 09 2001.
Richard Schroeppel communicated Jensen's calculation of the first 56 terms, Feb 21 2005
Gill Barequet commented on Madras's proof from 1999 of the limit growth rate of this sequence, and provided references to the currently bestknown bounds on it, May 24, 2011.


STATUS

approved



