cp's OEIS Frontend

A221938 Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out straight through or left turns.

%I A221938 #8 Aug 11 2018 13:09:33
%S A221938 1,17,105,783,5622,40608,293084,2115379,15268366,110202874,795416273,
%T A221938 5741108247,41437835079,299087573904,2158736742330,15581203397143,
%U A221938 112461095655909,811715097631008,5858749604657939,42286939137094085
%N A221938 Number of 2 X n arrays of occupancy after each element stays put or moves to some horizontal or antidiagonal neighbor, without move-in move-out straight through or left turns.
%C A221938 Row 2 of A221937.
%H A221938 R. H. Hardin, <a href="/A221938/b221938.txt">Table of n, a(n) for n = 1..210</a>
%F A221938 Empirical: a(n) = 3*a(n-1) + 25*a(n-2) + 40*a(n-3) + a(n-4) - 42*a(n-5) - 20*a(n-6) + 10*a(n-7) + 4*a(n-8) -a(n-9).
%F A221938 Empirical g.f.: x*(1 + 14*x + 29*x^2 + 3*x^3 - 33*x^4 - 8*x^5 + 19*x^6 + 4*x^7 - x^8) / (1 - 3*x - 25*x^2 - 40*x^3 - x^4 + 42*x^5 + 20*x^6 - 10*x^7 - 4*x^8 + x^9). - _Colin Barker_, Aug 11 2018
%e A221938 Some solutions for n=3:
%e A221938 ..0..4..0....1..2..0....1..0..2....2..0..0....0..3..0....0..3..2....0..3..1
%e A221938 ..0..2..0....0..2..1....1..2..0....0..3..1....2..0..1....0..0..1....0..1..1
%Y A221938 Cf. A221937.
%K A221938 nonn
%O A221938 1,2
%A A221938 _R. H. Hardin_, Feb 01 2013