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A066158
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Number of fixed polyominoes with n cells and tree-like structure.
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11
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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
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1,2
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COMMENTS
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Computed by a modified version of the program used for A065068.
Aleksandrowicz and Barequet (2011) confirm first 27 terms. [Gill Barequet, May 25 2011]
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REFERENCES
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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, Springer-Verlag, 90-99, 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) 5327-5350.
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LINKS
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CROSSREFS
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Cf. A001168 (fixed polyominoes), A019441 (coefficients of g.f. related to this sequence), A118356, A191094, A191095, A191096, A191097, A191098 (fixed tree-like polycubes in 3, 4, 5, 6, 7, and 8 dimensions, resp.).
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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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.
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STATUS
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approved
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