A251084 - OEIS

%I #8 Nov 24 2018 12:05:34

%S 420,1306,2362,4718,8512,15780,28616,52934,98550,186788,358250,695798,

%T 1363076,2688996,5329268,10596902,21115770,42135172,84151526,

%U 168159190,336144664,672082436,1343919232,2687549958,5374762142,10749132260

%N Number of (n+1) X (4+1) 0..2 arrays with no 2 X 2 subblock having the sum of its diagonal elements greater than the absolute difference of its antidiagonal elements.

%H R. H. Hardin, <a href="/A251084/b251084.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 6*a(n-1) - 13*a(n-2) + 10*a(n-3) + 5*a(n-4) - 14*a(n-5) + 9*a(n-6) - 2*a(n-7) for n>8.

%F Empirical g.f.: 2*x*(210 - 607*x - 7*x^2 + 1662*x^3 - 2125*x^4 + 886*x^5 + 53*x^6 - 89*x^7) / ((1 - x)^5*(1 + x)*(1 - 2*x)). - _Colin Barker_, Nov 24 2018

%e Some solutions for n=4:

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

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

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

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

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

%Y Column 4 of A251088.

%K nonn

%O 1,1

%A _R. H. Hardin_, Nov 29 2014