A248996 Number of length n+4 0..3 arrays with no five consecutive terms having two times the sum of any three elements equal to three times the sum of the remaining two.

820, 2668, 8680, 28240, 91888, 299044, 973204, 3167500, 10309372, 33554728, 109215076, 355477276, 1157029012, 3765974644, 12257760052, 39897482020, 129861371368, 422682950584, 1375781835724, 4478003930896, 14575364597464

Offset: 1

Author

R. H. Hardin, Oct 18 2014

Keywords

• nonn

Examples

			Some solutions for n=5:
..3....0....1....2....0....0....1....3....2....1....0....3....1....0....0....3
..0....2....0....0....3....0....2....2....2....0....0....1....2....1....3....0
..3....2....3....3....3....2....1....0....3....2....0....2....1....0....0....0
..1....0....0....1....1....2....0....0....2....0....2....0....0....2....0....1
..0....2....2....2....1....2....3....3....0....0....0....0....0....3....3....3
..2....2....3....0....3....3....2....3....0....0....1....1....3....1....3....2
..1....0....1....3....1....3....3....0....1....1....0....0....3....1....3....1
..3....3....1....3....1....2....1....1....3....3....1....0....0....1....2....0
..0....1....1....3....3....3....0....2....0....2....2....0....0....0....1....0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Column 3 of A249001.

Formula

Empirical: a(n) = 3*a(n-1) + 2*a(n-2) - a(n-3) - 9*a(n-4) + 16*a(n-5) - 48*a(n-6) - 21*a(n-7) + 8*a(n-8) + 3*a(n-9).

Empirical g.f.: 4*x*(205 + 52*x - 241*x^2 - 579*x^3 - 36*x^4 - 3382*x^5 - 1168*x^6 + 563*x^7 + 192*x^8) / (1 - 3*x - 2*x^2 + x^3 + 9*x^4 - 16*x^5 + 48*x^6 + 21*x^7 - 8*x^8 - 3*x^9). - Colin Barker, Nov 09 2018