

A006770


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


13



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

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



KEYWORD

nonn,hard,more


AUTHOR



EXTENSIONS



STATUS

approved



