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A006069

Number of directed Hamiltonian cycles (or Gray codes) on n-cube with a marked starting node.

2, 8, 96, 43008, 58018928640, 4587291356489073135452160

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OFFSET

1,1

COMMENTS

More precisely, this is the number of ways of making a list of the 2^n nodes of the n-cube, with a distinguished starting position and a direction, such that each node is adjacent to the previous one and the last node is adjacent to the first.

REFERENCES

M. Gardner, Knotted Doughnuts and Other Mathematical Entertainments. Freeman, NY, 1986, p. 24.

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=1..6.

H. Haanpaa and Patric R. J. Östergård, Counting Hamiltonian cycles in bipartite graphs, Math. Comp. 83 (2014), 979-995.

Michel Deza and Roman Shklyar, Enumeration of Hamiltonian Cycles in 6-cube, arXiv:1003.4391 [cs.DM], 2010. [There may be errors - see Haanpaa and Ostergard, 2012]

D. Sensarma, S. S. Sarma, GMDES: A graph based modified Data Encryption Standard algorithm with enhanced security, IJRET: International Journal of Research in Engineering and Technology 03:03 (2014), 653-660. See Section 2.2.

Eric Weisstein's World of Mathematics, Hamiltonian Cycle

Eric Weisstein's World of Mathematics, Hypercube Graph

FORMULA

a(n) = A003042(n)*2^n. - Max Alekseyev, Jun 15 2006

EXAMPLE

a(1) = 2: we have 1,2 or 2,1.

a(2) = 8: label the nodes 1, 2, ..., 4. Then the 8 possibilities are 1,2,3,4; 1,4,3,2; 2,3,4,1; 2,1,4,3; etc.

CROSSREFS

Cf. A003042, A006070, A091299, A091302, A159344.

Sequence in context: A361388 A326866 A001697 * A270485 A223042 A052457

Adjacent sequences: A006066 A006067 A006068 * A006070 A006071 A006072

KEYWORD