A225349 Number of 9Xn -1,1 arrays such that the sum over i=1..9,j=1..n of i*x(i,j) is zero, the sum of x(i,j) is zero, and rows are nondecreasing (number of ways to distribute n-across galley oarsmen left-right at 9 fore-aft positions so that there are no turning moments on the ship)

0, 181, 0, 6095, 0, 63121, 0, 364051, 0, 1478059, 0, 4749875, 0, 12917383, 0, 30996867, 0, 67483509, 0, 135917019, 0, 256859575, 0, 460336079, 0, 788783775, 0, 1300561813, 0, 2074066679, 0, 3212505371, 0, 4849371247, 0, 7154674999, 0, 10341975199, 0

Offset

1,2

Comments

Row 9 of A225345

Links

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

Formula

Empirical: a(n) = 2*a(n-2) -a(n-6) -a(n-10) +a(n-12) -a(n-14) +a(n-18) +a(n-20) +a(n-24) -2*a(n-26) -2*a(n-32) +a(n-34) +a(n-38) +a(n-40) -a(n-44) +a(n-46) -a(n-48) -a(n-52) +2*a(n-56) -a(n-58)

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...-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: A177327 A358413 A236235 * A074811 A036200 A357657

Adjacent sequences: A225346 A225347 A225348 * A225350 A225351 A225352

Keyword

nonn

Author

R. H. Hardin May 05 2013

Status

approved