login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo

Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 56th year, we are closing in on 350,000 sequences, and we’ve crossed 9,700 citations (which often say “discovered thanks to the OEIS”).

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A269644 Number of length-7 0..n arrays with no repeated value differing from the previous repeated value by other than plus two or minus 1. 1
20, 969, 9928, 55225, 216528, 675151, 1789528, 4200933, 8974480, 17780443, 33120936, 58606993, 99291088, 162060135, 256094008, 393394621, 589390608, 863622643, 1240514440, 1750234473, 2429653456, 3323402623, 4485037848 (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^7 + 7*n^6 + 6*n^5 + 20*n^4 - 22*n^3 + 28*n^2 - 37*n + 13 for n>2.

Conjectures from Colin Barker, Jan 25 2019: (Start)

G.f.: x*(20 + 809*x + 2736*x^2 + 1813*x^3 - 152*x^4 - 31*x^5 - 240*x^6 + 123*x^7 - 44*x^8 + 6*x^9)  / (1 - x)^8.

a(n) = 8*a(n-1) - 28*a(n-2) + 56*a(n-3) - 70*a(n-4) + 56*a(n-5) - 28*a(n-6) + 8*a(n-7) - a(n-8) for n>10.

(End)

EXAMPLE

Some solutions for n=3:

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

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

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

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

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

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

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

CROSSREFS

Row 7 of A269640.

Sequence in context: A269413 A274764 A069578 * A347856 A128482 A128476

Adjacent sequences:  A269641 A269642 A269643 * A269645 A269646 A269647

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 02 2016

STATUS

approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 2 13:15 EST 2021. Contains 349444 sequences. (Running on oeis4.)