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A199897 Number of -7..7 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative.

%I A199897 #7 Jul 22 2025 13:26:21
%S A199897 1,15,85,799,5839,51395,406575,3500269,28684325,245319361,2048301005,
%T A199897 17499467353,147731409251,1263413909311,10741266363733,92019265611439,
%U A199897 786112365529335,6747253002120179,57843127733658007,497375672047480891
%N A199897 Number of -7..7 arrays x(0..n-1) of n elements with zero sum, and adjacent elements not both strictly positive and not both strictly negative.
%C A199897 Column 7 of A199898
%H A199897 R. H. Hardin, <a href="/A199897/b199897.txt">Table of n, a(n) for n = 1..200</a>
%e A199897 Some solutions for n=6
%e A199897 ..1....3....2...-6...-4...-2...-7....2...-7....2....5...-6...-3....6....5....0
%e A199897 ..0...-4...-5....7....7....0....6...-4....1....0....0....1....0...-2....0....6
%e A199897 .-1....0....6...-4....0....0....0....7...-3....1...-1...-3....0....2...-7...-5
%e A199897 ..2....0...-7....2...-1....4...-6...-3....6...-7....0....4....7...-1....2....0
%e A199897 .-3...-2....7...-2....5...-5....0....1...-4....5....2...-3...-7....0...-3...-1
%e A199897 ..1....3...-3....3...-7....3....7...-3....7...-1...-6....7....3...-5....3....0
%K A199897 nonn
%O A199897 1,2
%A A199897 _R. H. Hardin_ Nov 11 2011