A255656 Number of length n+4 0..3 arrays with at most two downsteps in every 4 consecutive neighbor pairs.

968, 3692, 14192, 54560, 209412, 803246, 3083292, 11835664, 45429680, 174365744, 669261344, 2568836929, 9859943512, 37845226102, 145260624176, 557551963747, 2140043779888, 8214097736920, 31528047115872, 121013635650740

Offset: 1

Author

R. H. Hardin, Mar 01 2015

Keywords

• nonn

Comments

Column 4 of A255660

Examples

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

Links

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

Crossrefs

Cf. A255660

Formula

Empirical: a(n) = 4*a(n-1) -4*a(n-3) +15*a(n-4) -24*a(n-5) -68*a(n-6) +136*a(n-7) -81*a(n-8) +40*a(n-9) -10*a(n-10) +4*a(n-11) -a(n-12)