cp's OEIS Frontend

A221689 Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction.

%I A221689 #9 Aug 10 2018 17:33:28
%S A221689 6,152,3112,63676,1302720,26650988,545221260,11154026300,228186749552,
%T A221689 4668196767064,95500991265668,1953739262283024,39969188300499044,
%U A221689 817681276128120100,16727952148700884996,342216938625170086928
%N A221689 Number of n X 3 arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without consecutive moves in the same direction.
%C A221689 Column 3 of A221693.
%H A221689 R. H. Hardin, <a href="/A221689/b221689.txt">Table of n, a(n) for n = 1..210</a>
%F A221689 Empirical: a(n) = 24*a(n-1) - 69*a(n-2) - 71*a(n-3) + 2*a(n-4) for n>5.
%F A221689 Empirical g.f.: 2*x*(3 + 4*x - 61*x^2 - 49*x^3 + 2*x^4) / (1 - 24*x + 69*x^2 + 71*x^3 - 2*x^4). - _Colin Barker_, Aug 10 2018
%e A221689 Some solutions for n=3:
%e A221689 ..0..4..0....0..3..0....0..2..1....0..2..2....0..3..1....1..1..1....1..2..0
%e A221689 ..1..0..0....1..1..0....0..1..0....0..1..0....0..1..0....1..1..0....1..2..1
%e A221689 ..1..1..2....2..2..0....2..1..2....1..1..2....2..1..1....0..4..0....0..2..0
%Y A221689 Cf. A221693.
%K A221689 nonn
%O A221689 1,1
%A A221689 _R. H. Hardin_, Jan 22 2013