A239040 - OEIS

%I #7 Feb 24 2018 09:25:41

%S 3,7,16,38,90,212,500,1180,2784,6568,15496,36560,86256,203504,480128,

%T 1132768,2672544,6305344,14876224,35097536,82805760,195363968,

%U 460923008,1087457536,2565643008,6053132032,14281179136,33693644288,79493552640

%N Number of n X 1 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of elements above it, modulo 4.

%C Column 1 of A239047.

%H R. H. Hardin, <a href="/A239040/b239040.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 2*a(n-1) + 2*a(n-3).

%F Empirical g.f.: x*(3 + x + 2*x^2) / (1 - 2*x - 2*x^3). - _Colin Barker_, Feb 24 2018

%e Some solutions for n=5:

%e ..0....3....2....3....0....0....2....2....2....0....2....3....3....0....0....3

%e ..2....2....0....2....0....0....0....2....0....3....0....2....2....2....2....3

%e ..0....3....0....3....0....0....0....3....0....2....2....0....0....2....0....2

%e ..0....0....0....0....0....3....2....3....2....3....0....3....0....0....2....3

%e ..0....3....0....2....3....2....3....2....2....3....0....0....3....0....2....2

%Y Cf. A239047.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 09 2014