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A269436 Number of length-4 0..n arrays with no repeated value greater than the previous repeated value. 1
15, 78, 250, 615, 1281, 2380, 4068, 6525, 9955, 14586, 20670, 28483, 38325, 50520, 65416, 83385, 104823, 130150, 159810, 194271, 234025, 279588, 331500, 390325, 456651, 531090, 614278, 706875, 809565, 923056, 1048080, 1185393, 1335775 (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 + (11/2)*n^2 + (7/2)*n + 1.

Conjectures from Colin Barker, Jan 22 2019: (Start)

G.f.: x*(15 + 3*x + 10*x^2 - 5*x^3 + x^4) / (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:

..7. .8. .1. .4. .8. .5. .6. .6. .7. .0. .7. .7. .8. .5. .5. .0

..6. .3. .6. .3. .5. .3. .2. .4. .2. .7. .6. .1. .3. .3. .7. .3

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

..7. .2. .7. .0. .2. .1. .3. .4. .0. .8. .4. .6. .5. .0. .8. .1

CROSSREFS

Row 4 of A269435.

Sequence in context: A180579 A081591 A269620 * A044202 A044583 A212746

Adjacent sequences:  A269433 A269434 A269435 * A269437 A269438 A269439

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 26 2016

STATUS

approved

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Last modified April 22 16:32 EDT 2021. Contains 343177 sequences. (Running on oeis4.)