

A006770


Number of fixed ncelled polyominoes which need only touch at corners.
(Formerly M3565)


5



1, 4, 20, 110, 638, 3832, 23592, 147941, 940982, 6053180, 39299408, 257105146, 1692931066, 11208974860, 74570549714, 498174818986, 3340366308393
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OFFSET

1,2


COMMENTS

Also known as fixed polyplets.  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.
M. F. Hasler, Illustration of the A006770(3)=20 fixed 3polyplets, Sep 29 2014.
S. Mertens, Lattice animals: a fast enumeration algorithm and new perimeter polynomials, J. Stat. Phys. 58 (56) (1990) 10951108, 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.  David Bevan, Jul 28 2009
a(3)=20 counts 4 rotations (by 0°, 45°, 90°, 135°) of the straight ... trinomino, and 8 rotations (by multiples of 45°) of the Lshaped .: trinomino and the ..· 3polyplet, cf. link to the image.  M. F. Hasler, Sep 30 2014


CROSSREFS

Cf. A030222 (free polyplets).
Sequence in context: A026127 A222205 A153295 * A158827 A026156 A025183
Adjacent sequences: A006767 A006768 A006769 * A006771 A006772 A006773


KEYWORD

nonn,hard,more


AUTHOR

N. J. A. Sloane.


EXTENSIONS

One more term from Joseph Myers, Sep 26 2002


STATUS

approved



