login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A224019 Number of n X 3 0..3 arrays with rows nondecreasing and antidiagonals unimodal. 1
20, 400, 6796, 112436, 1859020, 30756756, 508916456, 8420768936, 139333478144, 2305467501680, 38147189410288, 631198698504112, 10444066884547776, 172811720487440320, 2859412053301829248, 47312978931444876928 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 3 of A224024.

LINKS

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

FORMULA

Empirical: a(n) = 20*a(n-1) - 70*a(n-2) + 228*a(n-3) - 276*a(n-4) + 392*a(n-5) - 196*a(n-6) + 144*a(n-7).

Empirical g.f.: 4*x*(5 + 49*x^2 - 11*x^3 + 85*x^4 - 13*x^5 + 36*x^6) / (1 - 20*x + 70*x^2 - 228*x^3 + 276*x^4 - 392*x^5 + 196*x^6 - 144*x^7). - Colin Barker, Aug 26 2018

EXAMPLE

Some solutions for n=3:

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

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

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

CROSSREFS

Cf. A224024.

Sequence in context: A057745 A224386 A189198 * A171294 A267793 A009964

Adjacent sequences:  A224016 A224017 A224018 * A224020 A224021 A224022

KEYWORD

nonn

AUTHOR

R. H. Hardin, Mar 30 2013

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 15 04:23 EST 2019. Contains 329991 sequences. (Running on oeis4.)