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 A006069 Number of directed Hamiltonian cycles (or Gray codes) on n-cube with a marked starting node. (Formerly M1903) 9
 2, 8, 96, 43008, 58018928640, 4587291356489073135452160 (list; graph; refs; listen; history; text; internal format)
 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 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: A156926 A326866 A001697 * A270485 A223042 A052457 Adjacent sequences:  A006066 A006067 A006068 * A006070 A006071 A006072 KEYWORD nonn,more AUTHOR EXTENSIONS a(5) corrected by Jonathan Cross (jcross(AT)wcox.com), Oct 10 2001 Definition corrected by Max Alekseyev, Jun 15 2006 a(6) from Michel Deza, Mar 28 2010 a(6) corrected by Haanpaa and Östergård, 2012. - N. J. A. Sloane, Sep 06 2012 STATUS approved

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Last modified June 18 17:27 EDT 2021. Contains 345120 sequences. (Running on oeis4.)