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A200873 Number of 0..n arrays x(0..4) of 5 elements without any interior element greater than both neighbors or less than both neighbors. 1
16, 77, 236, 567, 1168, 2163, 3704, 5973, 9184, 13585, 19460, 27131, 36960, 49351, 64752, 83657, 106608, 134197, 167068, 205919, 251504, 304635, 366184, 437085, 518336, 611001, 716212, 835171, 969152, 1119503, 1287648, 1475089, 1683408 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A200871.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = (1/60)*n^5 + (3/4)*n^4 + (15/4)*n^3 + (25/4)*n^2 + (127/30)*n + 1.

Conjectures from Colin Barker, Oct 16 2017: (Start)

G.f.: x*(16 - 19*x + 14*x^2 - 14*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

..0....1....2....0....0....1....1....1....2....3....3....2....1....3....0....2

..2....1....3....1....1....0....2....2....0....3....3....1....2....0....3....0

..2....1....3....3....3....0....3....3....0....0....1....1....2....0....3....0

..0....1....3....3....3....1....3....3....1....0....0....1....2....1....2....0

..0....0....0....1....0....1....3....2....2....2....0....1....2....1....2....2

CROSSREFS

Sequence in context: A007834 A228741 A346636 * A082966 A198182 A281466

Adjacent sequences:  A200870 A200871 A200872 * A200874 A200875 A200876

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 23 2011

STATUS

approved

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Last modified May 20 09:27 EDT 2022. Contains 353871 sequences. (Running on oeis4.)