A225313 Number of 6Xn -1,1 arrays such that the sum over i=1..6,j=1..n of i*x(i,j) is zero and rows are nondecreasing (ways to put n thrusters pointing east or west at each of 6 positions 1..n distance from the hinge of a south-pointing gate without turning the gate)

0, 35, 0, 443, 0, 2341, 0, 8221, 0, 22351, 0, 51521, 0, 105247, 0, 196779, 0, 342979, 0, 565693, 0, 891247, 0, 1352233, 0, 1986519, 0, 2839617, 0, 3963039, 0, 5417341, 0, 7269805, 0, 9598181, 0, 12487593, 0, 16035169, 0, 20345971, 0, 25538619, 0

Offset

1,2

Comments

Row 6 of A225310

Links

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

Formula

Empirical: a(n) = a(n-2) +a(n-4) -a(n-10) -2*a(n-14) +a(n-18) +a(n-20) +a(n-22) +a(n-24) -2*a(n-28) -a(n-32) +a(n-38) +a(n-40) -a(n-42)

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: A343981 A174593 A104785 * A028847 A365895 A176199

Adjacent sequences: A225310 A225311 A225312 * A225314 A225315 A225316

Keyword

nonn

Author

R. H. Hardin May 05 2013

Status

approved