

A006817


Trails of length n on square lattice.
(Formerly M3450)


2



1, 4, 12, 36, 108, 316, 916, 2628, 7500, 21268, 60092, 169092, 474924, 1329188, 3715244, 10359636, 28856252, 80220244, 222847804, 618083972, 1713283628, 4742946484, 13123882524, 36274940740, 100226653420, 276669062116, 763482430316, 2105208491748, 5803285527724
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OFFSET

0,2


COMMENTS

A trail is a path which may cross itself but does not reuse an edge. This sequence counts directed paths on the square lattice.


REFERENCES

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


LINKS



CROSSREFS

Undirected trailsrotation and reflection are counted by A001997.


KEYWORD

nonn,walk


AUTHOR



EXTENSIONS



STATUS

approved



