%I #7 Mar 22 2018 06:51:11
%S 0,8,112,1176,10976,96040,806736,6588344,52706752,415065672,
%T 3228288560,24857821912,189823367328,1439493868904,10851569165584,
%U 81386768741880,607687873272704,4519678557465736,33498794014157808,247518866882388248
%N Number of n X 1 0..7 arrays with some element plus some horizontally or vertically adjacent neighbor totalling seven exactly once.
%C Column 1 of A270118.
%H R. H. Hardin, <a href="/A270111/b270111.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 14*a(n-1) - 49*a(n-2).
%F Conjectures from _Colin Barker_, Mar 22 2018: (Start)
%F G.f.: 8*x^2 / (1 - 7*x)^2.
%F a(n) = 8*7^(n-2)*(n-1).
%F (End)
%e Some solutions for n=4:
%e ..5. .5. .6. .5. .0. .4. .7. .4. .4. .5. .7. .0. .7. .7. .1. .5
%e ..6. .5. .2. .2. .7. .3. .1. .3. .5. .2. .1. .4. .6. .2. .3. .0
%e ..7. .2. .2. .2. .1. .3. .6. .1. .3. .4. .6. .3. .1. .6. .4. .7
%e ..0. .3. .5. .3. .2. .6. .6. .5. .4. .0. .7. .6. .7. .1. .5. .7
%Y Cf. A270118.
%K nonn
%O 1,2
%A _R. H. Hardin_, Mar 11 2016