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A269410 Number of length-4 0..n arrays with no repeated value greater than or equal to the previous repeated value. 1
9, 63, 222, 570, 1215, 2289, 3948, 6372, 9765, 14355, 20394, 28158, 37947, 50085, 64920, 82824, 104193, 129447, 159030, 193410, 233079, 278553, 330372, 389100, 455325, 529659, 612738, 705222, 807795, 921165, 1046064, 1183248, 1333497 (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) = n^4 + 4*n^3 + (7/2)*n^2 + (1/2)*n.

Conjectures from Colin Barker, Jan 21 2019: (Start)

G.f.: 3*x*(3 + 6*x - x^2) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) for n>5.

(End)

EXAMPLE

Some solutions for n=8:

..8. .3. .1. .0. .3. .0. .8. .2. .3. .1. .0. .4. .3. .5. .4. .6

..8. .8. .3. .5. .4. .2. .1. .4. .0. .5. .2. .4. .0. .6. .4. .8

..4. .7. .3. .8. .7. .2. .0. .5. .3. .3. .7. .0. .0. .1. .2. .0

..0. .8. .8. .7. .5. .8. .5. .8. .2. .8. .0. .0. .2. .1. .4. .2

CROSSREFS

Row 4 of A269409.

Sequence in context: A299579 A344526 A269641 * A178161 A015669 A202982

Adjacent sequences:  A269407 A269408 A269409 * A269411 A269412 A269413

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 25 2016

STATUS

approved

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Last modified October 17 12:08 EDT 2021. Contains 348048 sequences. (Running on oeis4.)