A255663 Number of length n+3 0..3 arrays with at most two downsteps in every n consecutive neighbor pairs

256, 1024, 4048, 14192, 42653, 112196, 265430, 577464, 1174730, 2262312, 4162792, 7370432, 12625472, 21014456, 34103820, 54115508, 84155145, 128505312, 192998760, 285488992, 416438559, 599648684, 853157474, 1200338032, 1671232268

Offset

1,1

Comments

Row 3 of A255660

Links

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

Formula

Empirical: a(n) = (1/39916800)*n^11 + (1/403200)*n^10 + (1/9072)*n^9 + (109/40320)*n^8 + (63421/1209600)*n^7 + (39319/57600)*n^6 + (1888387/362880)*n^5 + (24707/2240)*n^4 + (4099087/453600)*n^3 + (33487/525)*n^2 + (950843/6930)*n + 28 for n>1

Example

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

Crossrefs

Cf. A255660

Sequence in context: A220764 A135272 A205595 * A045034 A236911 A236904

Adjacent sequences: A255660 A255661 A255662 * A255664 A255665 A255666

Keyword

nonn

Author

R. H. Hardin, Mar 01 2015

Status

approved