A209376 1/4 the number of (n+1) X 3 0..2 arrays with every 2 X 2 subblock having distinct edge sums.

8, 17, 34, 80, 170, 410, 882, 2138, 4610, 11186, 24130, 58562, 126338, 306626, 661506, 1605506, 3463682, 8406530, 18136066, 44017154, 94961666, 230476802, 497225730, 1206792194, 2603507714, 6318845954, 13632143362, 33085906946, 71378829314

Offset

1,1

Comments

Column 2 of A209382.

Links

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

Formula

Empirical: a(n) = a(n-1) + 6*a(n-2) - 6*a(n-3) - 4*a(n-4) + 4*a(n-5).

Empirical g.f.: x*(8 + 9*x - 31*x^2 - 8*x^3 + 20*x^4) / ((1 - x)*(1 - 6*x^2 + 4*x^4)). - Colin Barker, Jul 09 2018

Example

Some solutions for n=4:
..1..2..2....2..1..2....1..0..1....0..1..0....0..0..2....0..2..2....2..1..2
..0..0..1....2..0..2....2..0..2....2..2..0....2..1..2....0..1..0....2..0..0
..1..2..2....1..0..1....1..0..1....0..1..0....0..0..2....0..2..2....2..1..2
..0..0..1....2..2..2....2..0..2....0..2..2....2..1..2....0..1..0....0..0..2
..1..2..2....0..1..0....2..1..2....0..1..0....2..0..2....2..2..2....2..1..2

Crossrefs

Cf. A209382.

Sequence in context: A077221 A226601 A106648 * A159696 A049713 A297728

Adjacent sequences: A209373 A209374 A209375 * A209377 A209378 A209379

Keyword

nonn

Author

R. H. Hardin, Mar 07 2012

Status

approved