A183713 1/20 of the number of (n+1) X 4 0..4 arrays with every 2 X 2 subblock strictly increasing clockwise or counterclockwise with one decrease.
12, 54, 224, 950, 4012, 16964, 71712, 303170, 1281664, 5418314, 22906232, 96837444, 409385940, 1730703022, 7316648160, 30931557950, 130764969444, 552816553732, 2337064300200, 9880075964922, 41768598769664, 176579193270290
Offset: 1
Keywords
Examples
Some solutions for 3 X 4: ..0..4..1..4....0..4..0..4....4..0..4..0....3..0..3..4....3..2..3..2 ..2..3..2..3....1..2..1..3....3..2..3..2....2..1..2..0....0..1..0..1 ..0..4..1..0....0..3..0..4....0..1..4..0....3..4..3..4....3..2..4..2 ... ...L..R..L.......L..R..L.......R..L..R.......R..L..R.......L..R..L... ...R..L..R.......R..L..R.......L..R..L.......L..R..L.......R..L..R...
Links
- R. H. Hardin, Table of n, a(n) for n = 1..200
Crossrefs
Cf. A183719.
Formula
Empirical: a(n) = 2*a(n-1) + 10*a(n-2) - 10*a(n-4) - 2*a(n-5) + a(n-6).
Empirical g.f.: 2*x*(6 + 15*x - 2*x^2 - 19*x^3 - 4*x^4 + 2*x^5) / ((1 - x)*(1 + x)*(1 - 2*x - 9*x^2 - 2*x^3 + x^4)). - Colin Barker, Apr 04 2018
Comments