A255665 Number of length n+5 0..3 arrays with at most two downsteps in every n consecutive neighbor pairs.

4096, 16384, 64257, 209412, 564600, 1324872, 2816673, 5555336, 10323148, 18270784, 31047630, 50967648, 81218758, 126125244, 191474454, 284921080, 416484596, 599158024, 849649115, 1189278300, 1645061412, 2251009232

Offset: 1

Author

R. H. Hardin, Mar 01 2015

Keywords

• nonn

Comments

Row 5 of A255660.

Examples

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

Links

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

Crossrefs

Cf. A255660.

Formula

Empirical: a(n) = (1/39916800)*n^11 + (11/3628800)*n^10 + (1/6048)*n^9 + (125/24192)*n^8 + (315821/1209600)*n^7 + (994223/172800)*n^6 + (4372667/72576)*n^5 + (6881047/36288)*n^4 + (208795429/151200)*n^3 - (13877413/12600)*n^2 - (30361/231)*n + 712 for n>3.