cp's OEIS Frontend

A221405 Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two.

%I A221405 #6 Jul 23 2025 01:53:01
%S A221405 4,44,436,4518,47156,492102,5133044,53529806,558164472,5819704716,
%T A221405 60677191216,632619159318,6595610902832,68764677891112,
%U A221405 716926331557236,7474513869766556,77927543824707370,812454058048811426
%N A221405 Number of nX4 arrays of occupancy after each element stays put or moves to some horizontal or vertical neighbor, with every occupancy equal to zero or two.
%C A221405 Column 4 of A221408
%H A221405 R. H. Hardin, <a href="/A221405/b221405.txt">Table of n, a(n) for n = 1..94</a>
%F A221405 Empirical: a(n) = 19*a(n-1) -110*a(n-2) +250*a(n-3) -446*a(n-4) +939*a(n-5) -1112*a(n-6) -343*a(n-7) -822*a(n-8) +692*a(n-9) +1957*a(n-10) +2810*a(n-11) -1975*a(n-12) -59*a(n-13) -2679*a(n-14) +738*a(n-15) +1088*a(n-16) +1258*a(n-17) -418*a(n-18) -562*a(n-19) +192*a(n-20) +336*a(n-21) +32*a(n-22) -32*a(n-23)
%e A221405 Some solutions for n=3
%e A221405 ..0..2..2..0....0..2..0..2....2..2..0..2....2..2..0..2....0..2..0..0
%e A221405 ..2..2..0..0....0..2..0..2....0..0..0..2....0..2..0..0....2..0..0..2
%e A221405 ..0..0..2..2....2..0..0..2....2..2..0..0....2..0..2..0....2..2..2..0
%K A221405 nonn
%O A221405 1,1
%A A221405 _R. H. Hardin_ Jan 15 2013