cp's OEIS Frontend

A222549 Number of (n+2) X 1 arrays of occupancy after each element moves up to +-2 places but not 0.

%I A222549 #9 Aug 16 2018 08:58:33
%S A222549 7,20,64,208,651,2056,6496,20483,64627,203905,643272,2029453,6402679,
%T A222549 20199560,63726952,201050056,634285971,2001087460,6313163200,
%U A222549 19917184799,62836052203,198239333473,625418559696,1973111833705,6224903700199
%N A222549 Number of (n+2) X 1 arrays of occupancy after each element moves up to +-2 places but not 0.
%C A222549 Column 2 of A222555.
%H A222549 R. H. Hardin, <a href="/A222549/b222549.txt">Table of n, a(n) for n = 1..147</a>
%F A222549 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 A222549 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 A222549 Some solutions for n=3:
%e A222549 ..0....0....0....0....2....0....0....1....0....1....0....1....2....2....1....1
%e A222549 ..3....1....2....2....0....1....1....1....0....2....0....1....2....1....0....2
%e A222549 ..2....4....1....1....2....2....3....0....3....0....1....0....0....1....1....1
%e A222549 ..0....0....2....1....1....0....0....2....1....2....2....1....1....1....1....0
%e A222549 ..0....0....0....1....0....2....1....1....1....0....2....2....0....0....2....1
%Y A222549 Cf. A222555.
%K A222549 nonn
%O A222549 1,1
%A A222549 _R. H. Hardin_, Feb 24 2013