A239333 Number of n X 1 0..3 arrays with no element equal to one plus the sum of elements to its left or three plus the sum of elements above it, modulo 4.
2, 5, 12, 28, 66, 156, 368, 868, 2048, 4832, 11400, 26896, 63456, 149712, 353216, 833344, 1966112, 4638656, 10944000, 25820224, 60917760, 143723520, 339087488, 800010496, 1887468032, 4453111040, 10506243072, 24787422208, 58481066496
Offset: 1
Keywords
Examples
Some solutions for n=5: ..0....2....2....2....0....0....0....0....2....2....2....2....2....0....2....2 ..2....0....2....0....2....0....2....0....0....0....0....2....2....2....0....3 ..2....2....2....3....2....2....3....0....2....2....3....0....0....0....3....2 ..0....0....0....2....2....2....2....0....2....2....3....0....2....0....2....3 ..2....2....2....0....2....0....0....0....3....0....2....2....3....2....3....2
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Formula
Empirical: a(n) = 2*a(n-1) +2*a(n-3).
Empirical g.f.: (2 + x + 2*x^2) / (1 - 2*x - 2*x^3). - Colin Barker, Feb 18 2018
Comments