A225344 Number of nX8 -1,1 arrays such that the sum over i=1..n,j=1..8 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 8-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship).

1, 1, 5, 27, 171, 1081, 7261, 50659, 364051, 2676331, 20044255, 152452967, 1174757541, 9154016699, 72023900129, 571498084391, 4568690484153, 36765944370729, 297627015600415, 2422216988266317, 19808260648181603

Offset

1,3

Comments

Column 8 of A225345

Links

R. H. Hardin, Table of n, a(n) for n = 1..97

Example

Some solutions for n=4
.-1.-1.-1.-1..1..1..1..1...-1.-1.-1.-1..1..1..1..1...-1.-1.-1.-1.-1.-1..1..1
.-1.-1..1..1..1..1..1..1...-1.-1.-1.-1.-1.-1..1..1...-1.-1..1..1..1..1..1..1
.-1.-1.-1.-1.-1.-1.-1.-1....1..1..1..1..1..1..1..1...-1.-1..1..1..1..1..1..1
.-1.-1..1..1..1..1..1..1...-1.-1.-1.-1.-1.-1..1..1...-1.-1.-1.-1.-1.-1..1..1

Crossrefs

Sequence in context: A391647 A082425 A202248 * A109963 A201870 A091101

Adjacent sequences: A225341 A225342 A225343 * A225345 A225346 A225347

Keyword

nonn

Author

R. H. Hardin, May 05 2013

Status

approved