A224033 Number of n X 3 0..1 arrays with antidiagonals unimodal and rows and diagonals nondecreasing.
4, 13, 37, 105, 298, 848, 2419, 6908, 19737, 56401, 161181, 460622, 1316360, 3761867, 10750568, 30722673, 87798365, 250907593, 717036338, 2049125344, 5855930115, 16734904820, 47824518777, 136671503209, 390575802373, 1116176041318
Offset: 1
Keywords
Examples
Some solutions for n=3: ..0..0..1....0..0..0....0..0..0....0..0..0....0..0..0....0..1..1....0..0..0 ..0..1..1....1..1..1....0..0..1....0..0..0....0..0..0....1..1..1....0..1..1 ..1..1..1....0..1..1....1..1..1....0..0..1....0..1..1....1..1..1....0..1..1
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Cf. A224038.
Formula
Empirical: a(n) = 4*a(n-1) - 3*a(n-2) - a(n-3) + 2*a(n-5).
Empirical g.f.: x*(1 - x)*(4 + x - 2*x^2 - 2*x^3) / (1 - 4*x + 3*x^2 + x^3 - 2*x^5). - Colin Barker, Aug 26 2018
Comments