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!)
A200888 Number of 0..n arrays x(0..4) of 5 elements without any interior element greater than both neighbors. 1
21, 121, 422, 1121, 2507, 4977, 9052, 15393, 24817, 38313, 57058, 82433, 116039, 159713, 215544, 285889, 373389, 480985, 611934, 769825, 958595, 1182545, 1446356, 1755105, 2114281, 2529801, 3008026, 3555777, 4180351, 4889537, 5691632, 6595457 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Row 3 of A200886.
LINKS
FORMULA
Empirical: a(n) = (2/15)*n^5 + (11/6)*n^4 + (35/6)*n^3 + (23/3)*n^2 + (68/15)*n + 1.
Conjectures from Colin Barker, Oct 16 2017: (Start)
G.f.: x*(21 - 5*x + 11*x^2 - 16*x^3 + 6*x^4 - x^5) / (1 - x)^6.
a(n) = 6*a(n-1) - 15*a(n-2) + 20*a(n-3) - 15*a(n-4) + 6*a(n-5) - a(n-6) for n>6.
(End)
EXAMPLE
Some solutions for n=3
..3....3....3....2....0....1....0....3....1....3....3....2....2....2....0....2
..3....3....3....2....1....1....0....3....0....2....1....2....1....3....1....2
..3....3....2....3....1....0....0....2....0....3....3....0....0....3....1....2
..3....3....1....3....0....2....2....3....2....3....3....2....3....1....0....0
..2....0....1....2....3....2....3....3....3....3....0....2....3....2....1....0
CROSSREFS
Sequence in context: A325484 A365205 A361699 * A179441 A164785 A179956
KEYWORD
nonn
AUTHOR
R. H. Hardin, Nov 23 2011
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 28 21:57 EDT 2024. Contains 371254 sequences. (Running on oeis4.)