A222550 Number of (n+3) X 1 arrays of occupancy after each element moves up to +-3 places but not 0.

31, 102, 359, 1279, 4537, 15929, 56041, 197313, 694561, 2443809, 8598567, 30254246, 106446779, 374510087, 1317616614, 4635657529, 16309130459, 57378359687, 201866467555, 710197956209, 2498584711494, 8790394014302, 30925899907467

Offset: 1

Author

R. H. Hardin, Feb 24 2013

Keywords

• nonn

Comments

Column 3 of A222555.

Examples

			Some solutions for n=3:
..1....1....0....1....1....1....0....0....0....1....1....1....1....2....0....0
..0....0....2....1....0....1....2....1....3....2....0....0....0....1....1....0
..3....1....0....0....0....0....1....0....2....2....0....2....0....3....0....1
..0....3....2....0....1....3....1....3....0....1....3....1....1....0....3....0
..0....0....0....1....2....1....1....2....1....0....0....1....1....0....1....3
..2....1....2....3....2....0....1....0....0....0....2....1....3....0....1....2
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..131

Crossrefs

Cf. A222555.

Formula

Empirical: a(n) = 7*a(n-1) -15*a(n-2) +10*a(n-3) +4*a(n-4) -36*a(n-5) +73*a(n-6) -29*a(n-7) -21*a(n-8) -a(n-9).

Empirical g.f.: x*(31 - 115*x + 110*x^2 - 14*x^3 - 175*x^4 + 473*x^5 - 224*x^6 - 148*x^7 - 7*x^8) / (1 - 7*x + 15*x^2 - 10*x^3 - 4*x^4 + 36*x^5 - 73*x^6 + 29*x^7 + 21*x^8 + x^9). - Colin Barker, Aug 16 2018