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A269635 Number of length-n 0..3 arrays with no repeated value differing from the previous repeated value by other than plus two or minus 1. 1
4, 16, 60, 221, 796, 2828, 9928, 34537, 119236, 409098, 1396288, 4744671, 16062116, 54199810, 182382428, 612236251, 2050883956, 6857469364, 22892085300, 76311433969, 254067536796, 844941922160, 2807225267056, 9318543171653 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 9*a(n-1) - 21*a(n-2) - 19*a(n-3) + 93*a(n-4) + 27*a(n-5) - 133*a(n-6) - 87*a(n-7).

Empirical g.f.: x*(4 - 20*x + 93*x^3 - x^4 - 151*x^5 - 89*x^6) / ((1 - 3*x)*(1 - 6*x + 3*x^2 + 28*x^3 - 9*x^4 - 54*x^5 - 29*x^6)). - Colin Barker, Jan 25 2019

EXAMPLE

Some solutions for n=9:

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

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

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

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

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

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

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

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

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

CROSSREFS

Column 3 of A269640.

Sequence in context: A255303 A273347 A268939 * A267928 A269532 A269673

Adjacent sequences:  A269632 A269633 A269634 * A269636 A269637 A269638

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 02 2016

STATUS

approved

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Last modified December 9 09:37 EST 2021. Contains 349627 sequences. (Running on oeis4.)