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Number of (undirected) Hamiltonian paths on the triangular grid with n vertices on each side.
1

%I #9 Jan 19 2022 14:32:40

%S 1,3,12,114,1968,66312,4381020,578266212,153350225268,82409298702462,

%T 90180040305841212,201800030110625440248,926548406689594565864346,

%U 8752381854153235620928637604

%N Number of (undirected) Hamiltonian paths on the triangular grid with n vertices on each side.

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/HamiltonianPath.html">Hamiltonian Path</a>

%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/TriangularGridGraph.html">Triangular Grid Graph</a>

%F a(n) = A112675(n)/2 for n > 1.

%Y Cf. A112675, A112676, A266513, A288148.

%K nonn

%O 1,2

%A _Eric W. Weisstein_, May 14 2019

%E a(1) corrected by _Andrew Howroyd_, Jan 19 2022