A222549 - OEIS

%I #9 Aug 16 2018 08:58:33

%S 7,20,64,208,651,2056,6496,20483,64627,203905,643272,2029453,6402679,

%T 20199560,63726952,201050056,634285971,2001087460,6313163200,

%U 19917184799,62836052203,198239333473,625418559696,1973111833705,6224903700199

%N Number of (n+2) X 1 arrays of occupancy after each element moves up to +-2 places but not 0.

%C Column 2 of A222555.

%H R. H. Hardin, <a href="/A222549/b222549.txt">Table of n, a(n) for n = 1..147</a>

%F Empirical: a(n) = 5*a(n-1) - 6*a(n-2) + 2*a(n-3) - 8*a(n-4) + 12*a(n-5) - 3*a(n-6) - a(n-7).

%F Empirical g.f.: x*(7 - 15*x + 6*x^2 - 6*x^3 + 11*x^4 - 3*x^5 - x^6) / ((1 - x)*(1 - 4*x + 2*x^2 + 8*x^4 - 4*x^5 - x^6)). - _Colin Barker_, Aug 16 2018

%e Some solutions for n=3:

%e ..0....0....0....0....2....0....0....1....0....1....0....1....2....2....1....1

%e ..3....1....2....2....0....1....1....1....0....2....0....1....2....1....0....2

%e ..2....4....1....1....2....2....3....0....3....0....1....0....0....1....1....1

%e ..0....0....2....1....1....0....0....2....1....2....2....1....1....1....1....0

%e ..0....0....0....1....0....2....1....1....1....0....2....2....0....0....2....1

%Y Cf. A222555.

%K nonn

%O 1,1

%A _R. H. Hardin_, Feb 24 2013