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Number of 2Xn integer arrays with each element equal to the number of horizontal, diagonal and antidiagonal neighbors exactly one smaller than itself.
1

%I #4 Dec 21 2015 12:29:49

%S 1,9,25,49,149,625,2141,5433,17269,65249,214877,600025,1934485,

%T 6961153,22488637,66171721,214994149,746222545,2392193165,7273608601,

%U 23705004725,80233190113,256613628509,797094034921,2598493640773,8647653815601

%N Number of 2Xn integer arrays with each element equal to the number of horizontal, diagonal and antidiagonal neighbors exactly one smaller than itself.

%C Row 2 of A266131.

%H R. H. Hardin, <a href="/A266132/b266132.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = a(n-1) +8*a(n-3) +80*a(n-4) -40*a(n-5) -52*a(n-6) -112*a(n-7) -1204*a(n-8) +292*a(n-9) +64*a(n-10) -880*a(n-11) +4016*a(n-12) -2112*a(n-13) -1152*a(n-14) +1024*a(n-15) -4608*a(n-16) +4608*a(n-17)

%e Some solutions for n=4

%e ..1..2..0..1....1..1..1..2....1..1..1..1....1..1..0..1....0..2..0..1

%e ..0..0..1..1....0..0..1..2....1..0..0..1....1..0..2..0....1..0..1..1

%Y Cf. A266131.

%K nonn

%O 1,2

%A _R. H. Hardin_, Dec 21 2015