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A200874 Number of 0..n arrays x(0..5) of 6 elements without any interior element greater than both neighbors or less than both neighbors. 1
26, 163, 602, 1673, 3886, 7973, 14932, 26073, 43066, 67991, 103390, 152321, 218414, 305929, 419816, 565777, 750330, 980875, 1265762, 1614361, 2037134, 2545709, 3152956, 3873065, 4721626, 5715711, 6873958, 8216657, 9765838, 11545361 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 4 of A200871.

LINKS

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

FORMULA

Empirical: a(n) = (1/360)*n^6 + (7/24)*n^5 + (197/72)*n^4 + (185/24)*n^3 + (1667/180)*n^2 + 5*n + 1.

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

G.f.: x*(26 - 19*x + 7*x^2 - 28*x^3 + 22*x^4 - 7*x^5 + x^6) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.

(End)

EXAMPLE

Some solutions for n=3

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

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

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

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

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

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

CROSSREFS

Sequence in context: A232585 A042314 A280213 * A027280 A006354 A249292

Adjacent sequences:  A200871 A200872 A200873 * A200875 A200876 A200877

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 23 2011

STATUS

approved

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Last modified August 16 23:53 EDT 2022. Contains 356169 sequences. (Running on oeis4.)