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Number of (undirected) paths in the n-triangular grid graph.
4

%I #9 Jun 07 2017 20:16:29

%S 0,6,108,2598,123750,12994248,3114709914,1730766715308,

%T 2248937669398650,6877862090075063484,49790967547432817528562,

%U 857275977287938332061154856,35233501393224883314185777947590

%N Number of (undirected) paths in the n-triangular grid graph.

%C Paths of length zero are not counted here.

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

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

%e a(1) = 6:

%e : o : o : o : o : o : o

%e : : / : \ : / \ : \ : /

%e : o---o : o o : o o : o o : o---o : o---o .

%Y Cf. A020874, A266513, A112675, A112676.

%K nonn,more

%O 0,2

%A _Eric W. Weisstein_, Jun 05 2017

%E a(7)-a(12) from _Andrew Howroyd_, Jun 07 2017