A229013 Number of arrays of median of three adjacent elements of some length-5 0..n array, with no adjacent equal elements in the latter.
2, 15, 46, 101, 186, 307, 470, 681, 946, 1271, 1662, 2125, 2666, 3291, 4006, 4817, 5730, 6751, 7886, 9141, 10522, 12035, 13686, 15481, 17426, 19527, 21790, 24221, 26826, 29611, 32582, 35745, 39106, 42671, 46446, 50437, 54650, 59091, 63766, 68681, 73842
Offset: 1
Keywords
Examples
Some solutions for n=4: ..2....1....1....3....3....0....4....2....1....2....2....0....2....2....0....1 ..1....4....0....0....4....1....2....1....2....1....4....2....2....0....3....3 ..3....1....3....3....1....1....2....4....0....2....3....3....3....2....2....3
Links
- R. H. Hardin, Table of n, a(n) for n = 1..210
Crossrefs
Row 3 of A229012.
Formula
Empirical: a(n) = n^3 + 3*n^2 - 3*n + 1.
Conjectures from Colin Barker, Sep 13 2018: (Start)
G.f.: x*(2 - x)*(1 + 4*x + x^2) / (1 - x)^4.
a(n) = 4*a(n-1) - 6*a(n-2) + 4*a(n-3) - a(n-4) for n>4.
(End)
Comments