A217879 Number of n element 0..2 arrays with each element the minimum of 4 adjacent elements of a random 0..2 array of n+3 elements.

3, 9, 22, 46, 86, 153, 274, 511, 993, 1966, 3880, 7558, 14544, 27819, 53226, 102217, 197056, 380656, 735334, 1418931, 2734793, 5267460, 10145106, 19545576, 37670258, 72617646, 139990248, 269844980, 520094648, 1002351809, 1931757285, 3723025114

Offset: 1

Author

R. H. Hardin, Oct 14 2012

Keywords

• nonn

Comments

Column 4 of A217883.

Examples

			Some solutions for n=4:
..2....0....1....1....2....0....1....1....1....1....1....2....1....0....0....2
..2....0....1....2....2....1....1....2....1....1....1....1....2....2....1....2
..1....1....2....1....0....2....2....0....1....0....2....0....2....2....1....2
..0....1....1....0....0....2....2....0....2....0....0....0....2....0....2....2
		

Links

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

Crossrefs

Cf. A217883.

Formula

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

Empirical g.f.: x*(1 + x^2 + x^3 + x^4)*(3 + x^2 + x^3 + x^4) / (1 - 3*x + 3*x^2 - x^3 - 3*x^5 + x^6 - x^7 - x^8 - x^9). - Colin Barker, Jul 23 2018