

A007274


Walks on hexagonal lattice using each point at most twice.
(Formerly M4222)


1



1, 6, 36, 216, 1260, 7206, 40650, 227256, 1262832, 6983730, 38470224, 211220814, 1156489782, 6317095284, 34435495872, 187380150468, 1018035642054
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OFFSET

0,2


COMMENTS

The hexagonal lattice is the familiar 2dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
Guttman et al. has incorrect a(10) = 38470220, a(11) = 211220800, a(12) = 1156490000.  Sean A. Irvine, Dec 02 2017


REFERENCES

A. J. Guttmann, C. Byrnes and N. E. Frankel, A generalized selfavoiding walk, J. Phys. A 17 (1984), L457L461.
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=0..16.
G. Nebe and N. J. A. Sloane, Home page for hexagonal (or triangular) lattice A2


CROSSREFS

Cf. A001334, A007275.
Sequence in context: A124535 A267789 A228737 * A269616 A269580 A269432
Adjacent sequences: A007271 A007272 A007273 * A007275 A007276 A007277


KEYWORD

nonn,walk


AUTHOR

Simon Plouffe


EXTENSIONS

Title improved, a(10)a(12) corrected, and a(15)a(16) added by Sean A. Irvine, Dec 02 2017


STATUS

approved



