cp's OEIS Frontend

A208873 Number of 2 X n 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.

%I A208873 #9 Jul 07 2018 08:51:27
%S A208873 2,12,136,1798,24472,334618,4578580,62655190,857412640,11733394642,
%T A208873 160567489036,2197311225838,30069453572632,411490201499818,
%U A208873 5631102858140740,77059719245016070,1054535937228511120
%N A208873 Number of 2 X n 0..3 arrays with new values 0..3 introduced in row major order and no element equal to more than one of its immediate leftward or upward or right-upward antidiagonal neighbors.
%C A208873 Row 2 of A208872.
%H A208873 R. H. Hardin, <a href="/A208873/b208873.txt">Table of n, a(n) for n = 1..210</a>
%F A208873 Empirical: a(n) = 18*a(n-1) - 65*a(n-2) + 84*a(n-3) - 36*a(n-4) for n>5.
%F A208873 Empirical g.f.: 2*x*(1 - 12*x + 25*x^2 - 19*x^3 + 6*x^4) / ((1 - x)*(1 - 2*x)*(1 - 15*x + 18*x^2)). - _Colin Barker_, Jul 07 2018
%e A208873 Some solutions for n=4:
%e A208873 ..0..0..1..0....0..0..0..0....0..0..1..0....0..0..0..0....0..1..1..0
%e A208873 ..1..2..2..0....1..1..1..0....1..0..1..0....1..1..1..2....0..0..2..0
%Y A208873 Cf. A208872.
%K A208873 nonn
%O A208873 1,1
%A A208873 _R. H. Hardin_, Mar 02 2012