login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A269684 Number of length-n 0..2 arrays with no repeated value differing from the previous repeated value by plus or minus one modulo 2+1. 1
3, 9, 27, 75, 201, 525, 1347, 3411, 8553, 21285, 52659, 129675, 318153, 778269, 1899267, 4625955, 11249481, 27321525, 66285747, 160679451, 389217513, 942260205, 2280029379, 5514901875, 13334998953, 32235231429, 77906125107 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
FORMULA
Empirical: a(n) = 4*a(n-1) - 3*a(n-2) - 2*a(n-3).
Conjectures from Colin Barker, Jan 27 2019: (Start)
G.f.: 3*x*(1 - x) / ((1 - 2*x)*(1 - 2*x - x^2)).
a(n) = 3*(-2^(1+n) + (1-sqrt(2))^(1+n) + (1+sqrt(2))^(1+n)) / 2.
(End)
EXAMPLE
Some solutions for n=9:
..0. .2. .0. .2. .1. .0. .0. .2. .0. .1. .1. .1. .1. .0. .2. .2
..2. .0. .0. .0. .0. .0. .2. .2. .0. .2. .0. .0. .2. .1. .1. .1
..1. .2. .2. .1. .0. .0. .1. .1. .1. .0. .1. .2. .0. .0. .2. .0
..1. .2. .0. .2. .2. .1. .0. .2. .0. .2. .0. .0. .1. .1. .0. .0
..1. .2. .2. .0. .1. .2. .1. .2. .0. .1. .1. .0. .1. .0. .1. .0
..2. .0. .0. .1. .2. .1. .1. .0. .0. .1. .0. .0. .2. .2. .1. .0
..0. .1. .2. .0. .1. .0. .2. .1. .0. .2. .1. .0. .0. .1. .2. .1
..1. .2. .1. .2. .2. .1. .1. .2. .0. .0. .1. .0. .1. .0. .1. .0
..1. .1. .2. .1. .0. .2. .2. .1. .0. .1. .1. .2. .0. .2. .0. .2
CROSSREFS
Column 2 of A269690.
Sequence in context: A289658 A180238 A289693 * A330079 A361423 A135415
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 03 2016
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified March 5 08:03 EST 2024. Contains 370538 sequences. (Running on oeis4.)