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!)
A221510 Number of 0..3 arrays of length n with each element differing from at least one neighbor by 2 or more, starting with 0. 1
0, 2, 3, 12, 30, 89, 248, 706, 1995, 5652, 15998, 45297, 128240, 363074, 1027923, 2910236, 8239390, 23327177, 66043368, 186980482, 529374875, 1498754084, 4243238398, 12013359841, 34011950560, 96293859202, 272624979363 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Column 3 of A221515.
LINKS
FORMULA
Empirical: a(n) = a(n-1) +4*a(n-2) +3*a(n-3) +a(n-4).
Empirical g.f.: x^2*(2 + x + x^2) / ((1 + x)*(1 - 2*x - 2*x^2 - x^3)). - Colin Barker, Oct 18 2017
EXAMPLE
Some solutions for n=6
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..2....2....2....2....2....3....2....2....3....3....2....3....3....2....3....3
..3....0....2....1....2....0....0....3....1....3....3....2....0....1....2....3
..0....2....0....3....0....3....1....1....0....1....1....0....3....3....0....1
..3....2....2....0....3....0....3....1....3....3....0....3....3....3....0....0
..0....0....0....3....1....2....1....3....0....0....2....0....1....1....2....3
CROSSREFS
Sequence in context: A073618 A247651 A305746 * A109489 A169636 A105401
KEYWORD
nonn
AUTHOR
R. H. Hardin, Jan 18 2013
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 February 26 20:11 EST 2024. Contains 370352 sequences. (Running on oeis4.)