A255664 Number of length n+4 0..3 arrays with at most two downsteps in every n consecutive neighbor pairs.

1024, 4096, 16128, 54560, 155144, 385738, 864924, 1788660, 3467296, 6376160, 11223728, 19042353, 31307660, 50094036, 78275176, 119780409, 179919544, 265791268, 386792720, 555250782, 787198896, 1103326862, 1530135124

Offset: 1

Author

R. H. Hardin, Mar 01 2015

Keywords

• nonn

Comments

Row 4 of A255660

Examples

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

Links

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

Crossrefs

Cf. A255660

Formula

Empirical: a(n) = (1/39916800)*n^11 + (1/362880)*n^10 + (11/80640)*n^9 + (461/120960)*n^8 + (141551/1209600)*n^7 + (36127/17280)*n^6 + (14049449/725760)*n^5 + (18041057/362880)*n^4 + (35402863/302400)*n^3 + (1423187/10080)*n^2 + (1020871/3080)*n + 163 for n>2