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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A266429 Number of 3 X n binary arrays with rows and columns lexicographically nondecreasing and column sums nondecreasing. 1
4, 13, 39, 106, 259, 574, 1170, 2223, 3982, 6787, 11089, 17472, 26677, 39628, 57460, 81549, 113544, 155401, 209419, 278278, 365079, 473386, 607270, 771355, 970866, 1211679, 1500373, 1844284, 2251561, 2731224, 3293224, 3948505, 4709068, 5588037 (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) = (1/360)*n^6 + (1/40)*n^5 + (1/9)*n^4 + (7/24)*n^3 + (319/360)*n^2 + (101/60)*n + 1.

Conjectures from Colin Barker, Jan 09 2019: (Start)

G.f.: x*(4 - 15*x + 32*x^2 - 34*x^3 + 21*x^4 - 7*x^5 + x^6) / (1 - x)^7.

a(n) = 7*a(n-1) - 21*a(n-2) + 35*a(n-3) - 35*a(n-4) + 21*a(n-5) - 7*a(n-6) + a(n-7) for n>7.

(End)

EXAMPLE

Some solutions for n=4:

..0..0..0..1....0..1..1..1....0..0..0..1....0..0..1..1....0..0..0..0

..0..0..1..0....0..1..1..1....0..0..0..1....0..0..1..1....0..0..1..1

..0..0..1..1....1..0..0..1....0..0..0..1....0..1..1..1....1..1..0..0

CROSSREFS

Row 3 of A266428.

Sequence in context: A058693 A027076 A183112 * A105693 A215404 A290929

Adjacent sequences:  A266426 A266427 A266428 * A266430 A266431 A266432

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 29 2015

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 October 30 18:09 EDT 2020. Contains 338090 sequences. (Running on oeis4.)