cp's OEIS Frontend

A239851 Number of n X 1 0..3 arrays with no element equal to zero plus the sum of elements to its left or zero plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4.

%I A239851 #8 Feb 18 2018 08:33:29
%S A239851 2,2,4,6,8,14,20,30,48,70,108,166,248,382,580,878,1344,2038,3100,4726,
%T A239851 7176,10926,16628,25278,38480,58534,89036,135494,206104,313566,477092,
%U A239851 725774,1104224,1679958,2555772,3888406,5915688,8999950,13692500
%N A239851 Number of n X 1 0..3 arrays with no element equal to zero plus the sum of elements to its left or zero plus the sum of elements above it or one plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4.
%C A239851 Column 1 of A239858.
%H A239851 R. H. Hardin, <a href="/A239851/b239851.txt">Table of n, a(n) for n = 1..210</a>
%F A239851 Empirical: a(n) = a(n-2) +2*a(n-3).
%F A239851 Empirical g.f.: 2*x*(1 + x + x^2) / (1 - x^2 - 2*x^3). - _Colin Barker_, Feb 18 2018
%e A239851 All solutions for n=4:
%e A239851 ..3....3....2....2....2....3
%e A239851 ..2....2....3....3....3....2
%e A239851 ..3....3....3....2....3....2
%e A239851 ..2....3....3....2....2....2
%K A239851 nonn
%O A239851 1,1
%A A239851 _R. H. Hardin_, Mar 28 2014