A225346 Number of 6Xn -1,1 arrays such that the sum over i=1..6,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 6 fore-aft positions so that there are no turning moments on the ship)

0, 15, 0, 107, 0, 397, 0, 1081, 0, 2399, 0, 4675, 0, 8273, 0, 13641, 0, 21267, 0, 31731, 0, 45637, 0, 63697, 0, 86635, 0, 115291, 0, 150513, 0, 193269, 0, 244527, 0, 305383, 0, 376929, 0, 460389, 0, 556975, 0, 668043, 0, 794921, 0, 939097, 0, 1102023, 0, 1285311

Offset

1,2

Comments

Row 6 of A225345

Links

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

Formula

Empirical: a(n) = a(n-2) +2*a(n-4) -a(n-6) -2*a(n-8) +a(n-12) -a(n-14) +2*a(n-18) +a(n-20) -2*a(n-22) -a(n-24) +a(n-26)

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

Crossrefs

Sequence in context: A054670 A277929 A303231 * A225312 A370335 A333845

Adjacent sequences: A225343 A225344 A225345 * A225347 A225348 A225349

Keyword

nonn

Author

R. H. Hardin May 05 2013

Status

approved