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!)
A221516 Number of 0..n arrays of length 5 with each element differing from at least one neighbor by 2 or more, starting with 0. 1
0, 3, 30, 130, 381, 884, 1765, 3174, 5285, 8296, 12429, 17930, 25069, 34140, 45461, 59374, 76245, 96464, 120445, 148626, 181469, 219460, 263109, 312950, 369541, 433464, 505325, 585754, 675405, 774956, 885109, 1006590, 1140149, 1286560 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Row 5 of A221515.
LINKS
FORMULA
Empirical: a(n) = 1*n^4 - 1*n^3 - 10*n^2 + 33*n - 34 for n>3.
Conjectures from Colin Barker, Aug 06 2018: (Start)
G.f.: x^2*(3 + 15*x + 10*x^2 + x^3 - 6*x^4 + 2*x^5 - x^6) / (1 - x)^5.
a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>8.
(End)
EXAMPLE
Some solutions for n=6:
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..3....6....3....6....4....2....3....2....5....4....4....6....2....6....6....2
..5....2....4....2....6....3....3....0....6....1....0....0....0....4....5....3
..4....4....6....6....5....5....0....6....0....0....5....4....4....2....1....6
..6....6....4....4....0....3....4....1....2....5....0....2....0....4....4....0
CROSSREFS
Cf. A221515.
Sequence in context: A031205 A225018 A365290 * A174774 A020874 A161806
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 April 22 02:54 EDT 2024. Contains 371887 sequences. (Running on oeis4.)