

A213451


Number of fixed triangular strip polyedges with n edges.
(Formerly N1209)


0



3, 15, 69, 309, 1365, 5973, 25941, 112065, 482067, 2066583, 8834469, 37677603, 160367343
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OFFSET

1,1


REFERENCES

N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).


LINKS

Table of n, a(n) for n=1..13.
C. Domb, On the theory of cooperative phenomena in crystals, Advances in Phys., 9 (1960), 149361. See page 354.


FORMULA

Apparently, a(n) = A001334(n)/2 for n >= 1. It needs to be clarified whether the objects described by this sequence are equivalent to the selfavoiding walks on the hexagonal lattice together with a restriction on their orientation.  Hugo Pfoertner, Jul 24 2021


CROSSREFS

Cf. A001334, A151540, A151541.
Sequence in context: A325586 A304276 A217451 * A224749 A122558 A110211
Adjacent sequences: A213448 A213449 A213450 * A213452 A213453 A213454


KEYWORD

nonn,more


AUTHOR

N. J. A. Sloane, Jun 11 2012


EXTENSIONS

Better description and more terms from Joseph Myers, Jun 12 2012


STATUS

approved



