A200436 Number of -n..n arrays x(0..8) of 9 elements with zero sum and no two or three adjacent elements summing to zero

0, 6780, 270848, 3397130, 23380862, 111101654, 410475622, 1264140498, 3392223642, 8172417894, 18054265218, 37145223104, 72010763708, 132735430724, 234296453996, 398306196892, 655184386476, 1046825751528, 1629833368476

Offset

1,2

Comments

Row 6 of A200430

Links

R. H. Hardin, Table of n, a(n) for n = 1..39

Formula

Empirical: a(n) = (259723/2240)*n^8 - (2162653/5040)*n^7 + (1479629/1440)*n^6 - (642659/360)*n^5 + (6107509/2880)*n^4 - (1200571/720)*n^3 + (3930541/5040)*n^2 - (22719/140)*n

Example

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

Crossrefs

Sequence in context: A206096 A238911 A031832 * A250332 A121106 A046515

Adjacent sequences: A200433 A200434 A200435 * A200437 A200438 A200439

Keyword

nonn

Author

R. H. Hardin Nov 17 2011

Status

approved