A222459 Number of n X 3 0..7 arrays with no entry increasing mod 8 by 7 rightwards or downwards, starting with upper left zero.

49, 12943, 3418807, 903055069, 238535974201, 63007686842527, 16643060295393343, 4396153388210813341, 1161214600539946100449, 306727092854223318882703, 81019916083604999480935207

Offset: 1

Author

R. H. Hardin, Feb 21 2013

Keywords

• nonn

Comments

Column 3 of A222462.

Examples

			Some solutions for n=3:
..0..0..0....0..0..0....0..0..0....0..0..4....0..0..0....0..0..0....0..0..0
..1..6..3....3..6..3....4..5..2....0..6..0....2..3..4....3..6..1....0..4..6
..2..6..6....6..7..4....5..0..2....6..2..3....7..4..5....5..6..1....4..6..2
		

Links

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

Crossrefs

Cf. A222462.

Formula

Empirical: a(n) = 270*a(n-1) - 1547*a(n-2).

Conjectures from Colin Barker, Mar 15 2018: (Start)

G.f.: 7*x*(7 - 41*x) / (1 - 270*x + 1547*x^2).

a(n) = ((135-sqrt(16678))^n*(-5294+41*sqrt(16678)) + (135+sqrt(16678))^n*(5294+41*sqrt(16678))) / (442*sqrt(16678)).

(End)