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A245158 Number of length n 0..3 arrays with new values introduced in order from both ends. 1
1, 1, 2, 4, 9, 23, 65, 199, 653, 2275, 8313, 31439, 121637, 477307, 1888721, 7509799, 29940861, 119550419, 477742889, 1909988479, 7637856725, 30546970411, 122178444417, 488693854679, 1954733475629, 7818845822083, 31275198738905 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

FORMULA

Empirical: a(n) = 10*a(n-1) - 37*a(n-2) + 64*a(n-3) - 52*a(n-4) + 16*a(n-5) for n>6.

Conjectures from Colin Barker, Nov 03 2018: (Start)

G.f.: x*(1 - 9*x + 29*x^2 - 43*x^3 + 31*x^4 - 11*x^5) / ((1 - x)^2*(1 - 2*x)^2*(1 - 4*x)).

a(n) = (-64 - 27*2^(2+n) + 4^n + 12*(32+3*2^n)*n) / 576 for n>1.

(End)

EXAMPLE

Some solutions for n=7:

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

..0....0....1....0....1....1....1....1....1....1....1....0....0....1....1....1

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

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

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

..0....1....0....1....0....1....0....0....0....1....0....0....0....1....1....0

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

CROSSREFS

Column 3 of A245163.

Sequence in context: A092668 A164039 A014137 * A245159 A245160 A245161

Adjacent sequences:  A245155 A245156 A245157 * A245159 A245160 A245161

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 12 2014

STATUS

approved

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Last modified January 18 13:09 EST 2019. Contains 319271 sequences. (Running on oeis4.)