cp's OEIS Frontend

A208409 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 two of its immediate leftward or upward or right-upward antidiagonal neighbors.

%I A208409 #8 Jul 02 2018 14:13:10
%S A208409 2,15,182,2698,41914,658450,10370330,163422914,2575668586,40595679634,
%T A208409 639841707002,10084768380770,158949607034890,2505261257850802,
%U A208409 39486313909133978,622357842865595522,9809203406810575786
%N A208409 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 two of its immediate leftward or upward or right-upward antidiagonal neighbors.
%C A208409 Row 2 of A208408.
%H A208409 R. H. Hardin, <a href="/A208409/b208409.txt">Table of n, a(n) for n = 1..210</a>
%F A208409 Empirical: a(n) = 18*a(n-1) - 31*a(n-2) - 66*a(n-3) - 24*a(n-4) for n>6.
%F A208409 Empirical g.f.: x*(1 + x)*(2 - 23*x - 3*x^2 + 22*x^3 + 8*x^4) / ((1 - 3*x - 2*x^2)*(1 - 15*x - 12*x^2)). - _Colin Barker_, Jul 02 2018
%e A208409 Some solutions for n=4:
%e A208409 ..0..0..0..1....0..1..1..1....0..0..0..0....0..0..1..0....0..0..1..0
%e A208409 ..1..1..0..0....0..0..0..1....1..0..2..2....0..0..0..0....2..0..1..2
%Y A208409 Cf. A208408.
%K A208409 nonn
%O A208409 1,1
%A A208409 _R. H. Hardin_, Feb 26 2012