A212777 Half the number of 0..3 arrays of length n+2 with second differences nonzero.

28, 99, 350, 1238, 4379, 15490, 54793, 193821, 685609, 2425226, 8578828, 30346157, 107344412, 379712753, 1343169821, 4751236703, 16806698494, 59450861306, 210297394895, 743891565706, 2631390949017, 9308101672049, 32925839761497

Offset: 1

Author

R. H. Hardin, May 27 2012

Keywords

• nonn

Comments

Column 3 of A212782.

Examples

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

Links

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

Crossrefs

Cf. A212782.

Formula

Empirical: a(n) = 2*a(n-1) + 5*a(n-2) + 3*a(n-3) - 4*a(n-4) - 4*a(n-5).

Empirical g.f.: x*(28 + 43*x + 12*x^2 - 41*x^3 - 32*x^4) / (1 - 2*x - 5*x^2 - 3*x^3 + 4*x^4 + 4*x^5). - Colin Barker, Jul 21 2018