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A078674 Number of ways to lace a shoe that has n pairs of eyelets, assuming the lacing satisfies certain conditions. 1
1, 3, 50, 2122, 155712, 17441962 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

The lace must follow a Hamiltonian path through the 2n eyelets and cannot pass in order though three adjacent eyelets that are in a line.

The lace is "undirected": reversing the order of eyelets along the path does not count as a different solution (cf. A078629).

LINKS

Table of n, a(n) for n=1..6.

Index entries for sequences related to shoe lacings

CROSSREFS

Apart from initial term, A078629/2.

Sequence in context: A279970 A217767 A185157 * A071094 A144987 A304055

Adjacent sequences:  A078671 A078672 A078673 * A078675 A078676 A078677

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Dec 16 2002

STATUS

approved

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Last modified February 16 09:23 EST 2019. Contains 320161 sequences. (Running on oeis4.)