

A066158


Number of fixed polyominoes with n cells and treelike structure.


11



1, 2, 6, 18, 55, 174, 570, 1908, 6473, 22202, 76886, 268352, 942651, 3329608, 11817582, 42120340, 150682450, 540832274, 1946892842, 7027047848, 25424079339, 92185846608, 334925007128, 1219054432490, 4444545298879, 16229462702152, 59347661054364
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OFFSET

1,2


COMMENTS

Computed by a modified version of the program used for A065068.
Aleksandrowicz and Barequet (2011) confirm first 27 terms. [Gill Barequet, May 25 2011]


REFERENCES

G. Aleksandrowicz and G. Barequet, Parallel enumeration of lattice animals, Proc. 5th Int. Frontiers of Algorithmics Workshop, Zhejiang, China, Lecture Notes in Computer Science, 6681, SpringerVerlag, 9099, May 2011.
N. Madras, C. E. Soteros, S. G. Whittington, J. L. Martin, M. F. Sykes et al., The free energy of a collapsing branched polymer, J. Phys. A: Math. Gen. 23 (1990) 53275350


LINKS

I. Jensen, Table of n, a(n) for n = 1..44 [From the arXiv paper]
I. Jensen, Enumerations of lattice animals and trees, J. Stat. Phys. 103 (34) (2001) 865881, Table II.
I. Jensen, Enumerations of lattice animals and trees, arXiv:condmat/0007239.


CROSSREFS

Cf. A001168 (fixed polyominoes), A019441 (coefficients of g.f. related to this sequence), A118356 / A191094 / A191095 / A191096 / A191097 / A191098 (fixed treelike polycubes in 3, 4, 5, 6, 7, and 8 dimensions, resp.).
Sequence in context: A294159 A000778 A006725 * A148456 A148457 A182881
Adjacent sequences: A066155 A066156 A066157 * A066159 A066160 A066161


KEYWORD

nonn


AUTHOR

Jan Kristian Haugland, Dec 13 2001


EXTENSIONS

Added a(18) and a(19) from Madras et al.  R. J. Mathar, Apr 08 2006
Terms from a(20) on added by N. J. A. Sloane, Nov 05 2008, from the Jensen paper.


STATUS

approved



