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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,4

COMMENTS

Or, number of 2-sided 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. 310-339 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

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Last modified November 15 05:50 EST 2019. Contains 329144 sequences. (Running on oeis4.)