%I M4203 #19 Aug 15 2020 08:12:46
%S 1,6,30,150,738,3570,17118,81498,385710,1817046,8528478,39903462,
%T 186198642,866861394,4027766490,18681900270,86518735722,400136695074,
%U 1848320799438,8528448008214
%N Trails of length n on hexagonal lattice.
%C The hexagonal lattice is the familiar 2dimensional lattice in which each point has 6 neighbors. This is sometimes called the triangular lattice.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H A. J. Guttmann, <a href="http://dx.doi.org/10.1088/03054470/18/4/009">Lattice trails II: numerical results</a>, J. Phys. A 22 (1989), 575588.
%H G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwthaachen.de/~Gabriele.Nebe/LATTICES/A2.html">Home page for hexagonal (or triangular) lattice A2</a>
%K nonn,walk,more
%O 0,2
%A _N. J. A. Sloane_.
%E a(17)a(19) from _Sean A. Irvine_, Aug 15 2020
