%I #4 Nov 06 2012 17:44:00

%S 1,15,61,249,993,3969,15871,63467,253797,1014889,4058377,16228793,

%T 64896323,259509919,1037738269,4149747805,16594171517,66357412857,

%U 265352580967,1061102131539,4243176114789,16967776245057,67851397847697

%N Hilltop maps: number of 2Xn binary arrays indicating the locations of corresponding elements not exceeded by any horizontal or antidiagonal neighbor in a random 0..3 2Xn array

%C Row 2 of A218810

%H R. H. Hardin, <a href="/A218811/b218811.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) +3*a(n-2) +3*a(n-3) +3*a(n-4) +3*a(n-5) +a(n-6) +5*a(n-7) +2*a(n-8) +2*a(n-9) +2*a(n-10) +2*a(n-11) +a(n-12) +a(n-13) -a(n-14) -a(n-15) -a(n-16) -a(n-17) -a(n-18) -a(n-19) for n>20

%e Some solutions for n=3

%e ..0..1..1....1..1..1....0..1..0....0..0..0....1..1..1....1..0..1....0..0..0

%e ..1..0..0....1..1..1....1..1..0....1..1..0....0..1..1....0..1..1....1..1..1

%K nonn

%O 1,2

%A _R. H. Hardin_ Nov 06 2012