A225343 Number of nX7 -1,1 arrays such that the sum over i=1..n,j=1..7 of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute 7-across galley oarsmen left-right at n fore-aft positions so that there are no turning moments on the ship)

0, 0, 0, 22, 0, 0, 0, 25056, 0, 0, 0, 47084448, 0, 0, 0, 110202390974, 0, 0, 0, 291612344834026, 0, 0, 0, 834664320724959518, 0, 0, 0, 2522954614267660110474, 0, 0, 0, 7938386813443913197221460, 0, 0, 0, 25757964315025150183357153902, 0, 0, 0

Offset

1,4

Comments

Column 7 of A225345

Links

R. H. Hardin, Table of n, a(n) for n = 1..105

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

Crossrefs

Sequence in context: A104787 A023922 A022064 * A252670 A297813 A156462

Adjacent sequences: A225340 A225341 A225342 * A225344 A225345 A225346

Keyword

nonn

Author

R. H. Hardin May 05 2013

Status

approved