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

0,2

COMMENTS

The hexagonal lattice is the familiar 2-dimensional 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 self-avoiding walk, J. Phys. A 17 (1984), L457-L461.

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

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Last modified October 25 20:31 EDT 2021. Contains 348256 sequences. (Running on oeis4.)