This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A222199 #29 Feb 16 2025 08:33:19
%S A222199 48,1344,23580,3273360,257165468,171785923808,61997157648756,
%T A222199 196554899918485160
%N A222199 Number of Hamiltonian cycles in the graph C_n X C_n.
%C A222199 C_n X C_n is also known as the (n,n)-torus grid graph.
%H A222199 Artem M. Karavaev, <a href="https://web.archive.org/web/20161024010518/http://flowproblem.ru/cycles/hamilton-cycles">Hamilton Cycles</a>.
%H A222199 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HamiltonianCycle.html">Hamiltonian Cycle</a>.
%H A222199 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TorusGridGraph.html">Torus Grid Graph</a>.
%t A222199 Table[Length[FindHamiltonianCycle[GraphProduct[CycleGraph[n], CycleGraph[n], "Cartesian"], All]], {n, 3, 6}] (* _Eric W. Weisstein_, Dec 16 2023 *)
%Y A222199 Cf. A270273, A003763, A222197, A268838, A222198, A193153, A270247.
%K A222199 nonn,hard,more
%O A222199 3,1
%A A222199 _N. J. A. Sloane_, Feb 14 2013