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A006770 Number of fixed n-celled polyominoes which need only touch at corners.
(Formerly M3565)
4
1, 4, 20, 110, 638, 3832, 23592, 147941, 940982, 6053180, 39299408, 257105146, 1692931066, 11208974860, 74570549714, 498174818986, 3340366308393 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also known as fixed polyplets [From David Bevan, Jul 28 2009]

REFERENCES

D. H. Redelmeier, personal communication.

N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

LINKS

Table of n, a(n) for n=1..17.

S. Mertens, Lattice animals: a fast enumeration algorithm and new perimeter polynomials, J. Stat. Phys. 58 (5-6) (1990) 1095-1108, Table 1.

Eric Weisstein's World of Mathematics, Polyplet.

EXAMPLE

a(2)=4: the two fixed dominoes and the two rotations of the polyplet consisting of two cells touching at a vertex [From David Bevan, Jul 28 2009]

CROSSREFS

Cf. A030222 (free polyplets) [From David Bevan, Jul 28 2009]

Sequence in context: A026127 A222205 A153295 * A158827 A026156 A025183

Adjacent sequences:  A006767 A006768 A006769 * A006771 A006772 A006773

KEYWORD

nonn,hard

AUTHOR

N. J. A. Sloane.

EXTENSIONS

One more term from Joseph Myers, Sep 26 2002

STATUS

approved

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Last modified July 26 01:07 EDT 2014. Contains 244923 sequences.