

A002013


Filaments with n square cells.
(Formerly M0835 N0317)


4



1, 1, 1, 2, 3, 7, 13, 31, 65, 154, 347, 824, 1905, 4512, 10546, 24935, 58476, 138002, 323894, 763172, 1790585, 4213061, 9878541, 23214728, 54393063, 127687369, 298969219
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OFFSET

0,4


COMMENTS

Or, number of 2sided strip polyominoes with n cells.  Ed Pegg Jr, May 13 2009


REFERENCES

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).
R. C. Tilley, R. G. Stanton and D. D. Cowan, The cell growth problem for filaments, pp. 310339 in Proceedings of the Louisiana Conference on Combinatorics, Graph Theory and Computer Science. Vol. 1, edited R. C. Mullin et al., 1970.


LINKS

Table of n, a(n) for n=0..26.
Ed Pegg, Jr., Illustrations of polyforms
Herman Tulleken, Polyominoes 2.2: How they fit together, (2019).
Eric Weisstein's World of Mathematics, Polyomino


CROSSREFS

Sequence in context: A102644 A014234 A124430 * A171416 A193530 A003120
Adjacent sequences: A002010 A002011 A002012 * A002014 A002015 A002016


KEYWORD

nonn


AUTHOR

N. J. A. Sloane


EXTENSIONS

a(23) from Joseph Myers, Nov 22 2010
a(24)a(26) from Sean A. Irvine, May 21 2013


STATUS

approved



