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A269651 Number of length-n 0..3 arrays with no adjacent pair x,x+1 repeated. 1
4, 16, 64, 253, 988, 3816, 14596, 55344, 208196, 777582, 2885120, 10640607, 39027196, 142415244, 517252820, 1870499543, 6736838192, 24172420350, 86428990624, 308016010824, 1094338584760, 3876828265788, 13696906252336 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A269656.

LINKS

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

FORMULA

Empirical: a(n) = 16*a(n-1) -108*a(n-2) +408*a(n-3) -986*a(n-4) +1704*a(n-5) -2312*a(n-6) +2560*a(n-7) -2355*a(n-8) +1832*a(n-9) -1208*a(n-10) +672*a(n-11) -314*a(n-12) +120*a(n-13) -36*a(n-14) +8*a(n-15) -a(n-16)

EXAMPLE

Some solutions for n=8

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

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

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

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

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

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

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

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

CROSSREFS

Cf. A269656.

Sequence in context: A228980 A188714 A005755 * A077821 A215877 A206450

Adjacent sequences:  A269648 A269649 A269650 * A269652 A269653 A269654

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 02 2016

STATUS

approved

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Last modified October 25 16:58 EDT 2021. Contains 348255 sequences. (Running on oeis4.)