A222993 Number of n X 2 0..2 arrays with successive rows and columns fitting to straight lines with nondecreasing slope, with a single point array taken as having zero slope.
9, 50, 222, 867, 3123, 10660, 35064, 112373, 353517, 1097430, 3374226, 10302919, 31301991, 94757960, 286108908, 862258905, 2595165345, 7803321850, 23447714310, 70422834731, 211436276379, 634661150700, 1904721649632, 5715708452797
Offset: 1
Keywords
Examples
Some solutions for n=3: ..2..0....1..1....2..0....1..0....0..1....1..0....2..2....0..0....1..1....1..0 ..0..0....1..1....1..1....2..2....0..1....2..2....1..1....1..2....0..0....2..2 ..0..1....1..2....2..2....0..1....1..2....0..2....0..1....0..2....1..1....1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..33
Formula
Empirical: a(n) = 9*a(n-1) - 31*a(n-2) + 51*a(n-3) - 40*a(n-4) + 12*a(n-5).
Conjectures from Colin Barker, Feb 19 2018: (Start)
G.f.: x*(9 - 31*x + 51*x^2 - 40*x^3 + 12*x^4) / ((1 - x)^2*(1 - 2*x)^2*(1 - 3*x)).
a(n) = (-13 - 2^(6+n) + 3^(4+n) - 2*(1+2^(4+n))*n) / 4.
(End)
Comments