%I #5 Mar 18 2016 07:59:01
%S 0,3,15,126,1149,14220,230247,5038371,149342775,6042348225,
%T 334920898542,25514812957710,2677815021433239,387891078557649963,
%U 77665115899526565021,21520282031334054823482,8260471327759688131895343
%N Number of nXnXn triangular 0..1 arrays with some element plus some adjacent element totalling 1+1 exactly once.
%C Column 1 of A270509.
%H R. H. Hardin, <a href="/A270503/b270503.txt">Table of n, a(n) for n = 1..28</a>
%e Some solutions for n=4
%e .....0........0........1........1........1........1........0........0
%e ....1.1......1.0......0.1......1.0......0.0......0.0......0.0......1.0
%e ...0.0.0....0.0.0....1.0.0....0.0.0....0.0.1....1.0.0....0.0.1....0.0.0
%e ..0.1.0.0..1.1.0.0..0.0.0.1..1.0.0.0..1.0.0.1..1.0.1.0..1.0.1.0..1.1.0.1
%Y Cf. A270509.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 18 2016