A268940 Number of length-n 0..4 arrays with no repeated value unequal to the previous repeated value plus one mod 4+1.

5, 25, 120, 565, 2615, 11950, 54045, 242365, 1079240, 4777225, 21038595, 92244790, 402898865, 1753806625, 7611458520, 32945585965, 142262759615, 612991045150, 2636186279445, 11317111447765, 48506655275240, 207603081203425

Offset: 1

Author

R. H. Hardin, Feb 16 2016

Keywords

• nonn

Examples

			Some solutions for n=7:
..2. .0. .3. .2. .2. .4. .1. .2. .3. .2. .2. .1. .1. .1. .3. .2
..3. .4. .3. .1. .3. .0. .3. .1. .3. .4. .0. .0. .2. .4. .0. .1
..1. .3. .0. .3. .2. .3. .1. .3. .2. .4. .3. .1. .4. .1. .2. .1
..3. .4. .1. .1. .0. .4. .4. .1. .1. .3. .2. .2. .1. .1. .1. .4
..4. .0. .4. .4. .0. .0. .1. .4. .4. .4. .0. .2. .2. .4. .4. .1
..0. .0. .0. .0. .1. .2. .3. .3. .1. .3. .4. .4. .4. .0. .2. .4
..1. .3. .2. .1. .4. .3. .4. .3. .4. .0. .1. .0. .0. .2. .2. .0
		

Links

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

Crossrefs

Column 4 of A268944.

Formula

Empirical: a(n) = 7*a(n-1) - 7*a(n-2) - 20*a(n-3).

Empirical g.f.: 5*x*(1 - 2*x - 4*x^2) / ((1 - 4*x)*(1 - 3*x - 5*x^2)). - Colin Barker, Jan 17 2019