A199641 Number of n X 2 0..2 arrays with values 0..2 introduced in row major order and each element equal to one or two horizontal and vertical neighbors.
1, 3, 13, 60, 288, 1384, 6628, 31772, 152304, 730036, 3499340, 16773680, 80402532, 385399644, 1847365808, 8855120468, 42445929772, 203459338800, 975257291396, 4674775757500, 22407962058928, 107409807372276, 514855687878924
Offset: 1
Keywords
Examples
Some solutions for n=3: ..0..1....0..0....0..0....0..1....0..0....0..0....0..0....0..1....0..0....0..0 ..0..1....0..0....1..0....0..1....1..1....1..1....1..0....0..1....0..1....0..1 ..0..1....1..1....1..0....2..2....1..1....2..2....1..1....1..1....0..1....1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..200
Crossrefs
Cf. A199647.
Formula
Empirical: a(n) = 3*a(n-1) +7*a(n-2) +8*a(n-3) -8*a(n-5) for n>7.
Empirical g.f.: x*(1 - 3*x^2 - 8*x^3 - 7*x^4 + 4*x^5 + 4*x^6) / (1 - 3*x - 7*x^2 - 8*x^3 + 8*x^5). - Colin Barker, May 16 2018
Comments