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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
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
KEYWORD
nonn
AUTHOR
R. H. Hardin, Mar 02 2016
STATUS
approved

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Last modified May 28 00:20 EDT 2024. Contains 372900 sequences. (Running on oeis4.)