login
A269470
Number of length-6 0..n arrays with no repeated value equal to the previous repeated value.
1
22, 462, 3180, 13300, 41730, 108402, 246232, 505800, 960750, 1713910, 2904132, 4713852, 7377370, 11189850, 16517040, 23805712, 33594822, 46527390, 63363100, 84991620, 112446642, 146920642, 189780360, 242583000, 307093150, 385300422
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = n^6 + 6*n^5 + 11*n^4 + 4*n^3 - n^2 + n.
Conjectures from Colin Barker, Jan 23 2019: (Start)
G.f.: 2*x*(11 + 154*x + 204*x^2 - 14*x^3 + 5*x^4) / (1 - x)^7.
a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.
(End)
EXAMPLE
Some solutions for n=3:
..1. .2. .1. .2. .1. .2. .1. .0. .1. .3. .1. .0. .3. .0. .3. .2
..0. .3. .0. .1. .0. .0. .0. .3. .3. .0. .1. .2. .0. .2. .2. .1
..3. .3. .1. .2. .2. .1. .0. .0. .3. .1. .3. .1. .1. .0. .0. .0
..0. .1. .3. .2. .1. .3. .2. .3. .0. .0. .2. .1. .1. .3. .1. .1
..2. .1. .2. .0. .3. .1. .0. .2. .0. .0. .2. .3. .0. .2. .0. .0
..2. .0. .1. .0. .1. .2. .2. .3. .2. .1. .3. .3. .1. .2. .0. .2
CROSSREFS
Row 6 of A269467.
Sequence in context: A268460 A231659 A269681 * A162808 A212335 A342887
KEYWORD
nonn
AUTHOR
R. H. Hardin, Feb 27 2016
STATUS
approved