A198976 Number of n X 2 0..5 arrays with values 0..5 introduced in row major order and no element equal to any horizontal or vertical neighbor.

1, 4, 34, 481, 8731, 174454, 3603244, 75251971, 1577395861, 33105096904, 695065679254, 14595390246661, 306496273473391, 6436373295247354, 135163500079092064, 2838431127851480551, 59607037068329713321

Offset

1,2

Comments

Column 2 of A198982.

Links

R. H. Hardin, Table of n, a(n) for n = 1..200

Formula

Empirical: a(n) = 32*a(n-1) - 262*a(n-2) + 672*a(n-3) - 441*a(n-4).

Conjectures from Colin Barker, Feb 22 2018: (Start)

G.f.: x*(1 - 28*x + 168*x^2 - 231*x^3) / ((1 - x)*(1 - 3*x)*(1 - 7*x)*(1 - 21*x)).

a(n) = (189 + 56*3^n + 18*7^n + 21^n) / 504.

(End)

Example

Some solutions with all values from 0 to 5 for n=4:
..0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1....0..1
..2..3....2..3....2..3....2..3....2..3....2..3....2..3....2..0....2..0....2..0
..4..5....4..2....1..4....0..4....4..5....4..0....4..5....3..1....3..4....3..4
..2..0....0..5....0..5....2..5....1..2....0..5....0..4....4..5....5..2....0..5

Crossrefs

Cf. A198982.

Sequence in context: A368445 A208831 A294475 * A156325 A248654 A336495

Adjacent sequences: A198973 A198974 A198975 * A198977 A198978 A198979

Keyword

nonn

Author

R. H. Hardin, Nov 01 2011

Status

approved