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%I #7 Jul 24 2018 09:40:10
%S 7,57,449,3567,28305,224643,1782855,14149449,112295673,891223263,
%T 7073103393,56134970523,445509522567,3535741318617,28061053779825,
%U 222703718478543,1767465563243697,14027311885918707,111326343684867783
%N Hilltop maps: number of n X 3 binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..2 n X 3 array.
%C Column 3 of A218592.
%H R. H. Hardin, <a href="/A218587/b218587.txt">Table of n, a(n) for n = 1..210</a>
%F Empirical: a(n) = 7*a(n-1) + 7*a(n-2) + 3*a(n-3) + 3*a(n-4) + 3*a(n-5).
%F Empirical g.f.: x*(7 + 8*x + x^2 + 4*x^3 + x^4) / (1 - 7*x - 7*x^2 - 3*x^3 - 3*x^4 - 3*x^5). - _Colin Barker_, Jul 24 2018
%e Some solutions for n=3:
%e ..1..0..0....0..1..1....1..0..1....0..1..0....1..1..1....1..1..1....1..1..1
%e ..0..1..0....0..1..1....0..0..1....1..1..1....0..1..0....0..1..1....0..0..1
%e ..1..1..1....0..1..0....1..0..1....0..0..0....0..1..1....0..0..0....1..0..1
%Y Cf. A218592.
%K nonn
%O 1,1
%A _R. H. Hardin_, Nov 03 2012
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