Artem M. Karavaev and N. J. A. Sloane, Table of n, a(n) for n=1..13 [First 11 terms from Artem M. Karavaev, Sep 29 2010; a(12) and a(13) from Pettersson, 2014, added by N. J. A. Sloane, Jun 05 2015]
F. Faase, On the number of specific spanning subgraphs of the graphs G X P_n, Preliminary version of paper that appeared in Ars Combin. 49 (1998), 129-154.
J. L. Jacobsen, Exact enumeration of Hamiltonian circuits, walks and chains in two and three dimensions, J. Phys. A: Math. Theor. 40 (2007) 14667-14678
Artem M. Karavaev, Hamilton Cycles.
Ville H. Pettersson, Enumerating Hamiltonian Cycles, The Electronic Journal of Combinatorics, Volume 21, Issue 4, 2014.
Ville Pettersson, Graph Algorithms for Constructing and Enumerating Cycles and Related Structures, Dissertation, Aalto, Finland, 2015.
A. Pönitz, Computing invariants in graphs of small bandwidth, Mathematics in Computers and Simulation, 49(1999), 179-191
T. G. Schmalz, G. E. Hite and D. J. Klein, Compact self-avoiding circuits on two-dimensional lattices, J. Phys. A 17 (1984), 445-453.
N. J. A. Sloane, Illustration of a(2) = 6
Peter Tittmann, Enumeration in graphs: counting Hamilton cycles
Eric Weisstein's World of Mathematics, Grid Graph
Eric Weisstein's World of Mathematics, Hamiltonian Cycle
Ed Wynn, Enumeration of nonisomorphic Hamiltonian cycles on square grid graphs, arXiv preprint arXiv:1402.0545 [math.CO], 2014.
Index entries for sequences related to graphs, Hamiltonian
Two more terms from Andre Poenitz [André Pönitz] and Peter Tittmann (poenitz(AT)htwm.de), Mar 03 2003
a(8) from Herman Jamke (hermanjamke(AT)fastmail.fm), Nov 21 2006
a(9) and a(10) from Jesper L. Jacobsen (jesper.jacobsen(AT)u-psud.fr), Dec 12 2007