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%I #7 Jul 24 2018 09:38:59
%S 15,255,4095,65535,1048545,16776705,268427265,4294836225,68717379375,
%T 1099478066175,17591648997375,281466382974975,4503462111871425,
%U 72055393538292225,1152886292586266625,18446180616957722625
%N Hilltop maps: number of n X 4 binary arrays indicating the locations of corresponding elements not exceeded by any king-move neighbor in a random 0..3 n X 4 array.
%C Column 4 of A218242.
%H R. H. Hardin, <a href="/A218238/b218238.txt">Table of n, a(n) for n = 1..88</a>
%F Empirical: a(n) = 15*a(n-1) + 15*a(n-2) + 15*a(n-3) + 15*a(n-4) + 15*a(n-5) + 15*a(n-6) + 15*a(n-7).
%F Empirical g.f.: 15*x*(1 + x)^2*(1 + x^2)^2 / (1 - 15*x - 15*x^2 - 15*x^3 - 15*x^4 - 15*x^5 - 15*x^6 - 15*x^7). - _Colin Barker_, Jul 24 2018
%e Some solutions for n=3:
%e ..0..1..1..0....1..1..1..0....1..0..1..0....0..0..0..1....0..1..1..1
%e ..0..0..0..1....1..0..1..0....0..1..1..0....1..1..1..1....0..1..1..1
%e ..0..1..1..1....0..1..0..1....1..1..0..1....0..1..1..1....0..1..1..0
%Y Cf. A218242.
%K nonn
%O 1,1
%A _R. H. Hardin_, Oct 24 2012
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