%I #15 Feb 19 2024 14:18:07
%S 1,16,4032,15240192,851527696384,698020036891115520,
%T 8357968487643562314301440,1457789983634180266210347100143616,
%U 3696916888496244614672984462362519120379904,136132525681108593648158474136309868068849288394833920
%N Number of Eulerian cycles in the n-triangular grid graph.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/EulerianCycle.html">Eulerian Cycle</a>.
%H Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/TriangularGridGraph.html">Triangular Grid Graph</a>.
%Y Cf. A334555.
%K nonn
%O 1,2
%A _Eric W. Weisstein_, Dec 29 2017
%E a(5)-a(9) from _Andrew Howroyd_, Jan 11 2018
%E a(10) from _Andrew Howroyd_, Feb 18 2024