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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A225308 Number of nX7 -1,1 arrays such that the sum over i=1..n,j=1..7 of i*x(i,j) is zero and rows are nondecreasing (ways to put 7 thrusters pointing east or west at each of n positions 1..n distance from the hinge of a south-pointing gate without turning the gate) 1
0, 0, 22, 122, 0, 0, 29638, 197440, 0, 0, 64811436, 458450486, 0, 0, 170747302728, 1245085560292, 0, 0, 497500354657954, 3694982212755606, 0, 0, 1544103180477715700, 11609994393282630090, 0, 0, 5004924971984927428464 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

COMMENTS

Column 7 of A225310

LINKS

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

EXAMPLE

Some solutions for n=4

.-1.-1.-1.-1.-1.-1.-1...-1.-1.-1.-1.-1.-1..1...-1.-1.-1..1..1..1..1

.-1.-1.-1.-1.-1..1..1...-1.-1.-1.-1.-1.-1.-1...-1.-1..1..1..1..1..1

.-1.-1.-1.-1.-1.-1..1...-1..1..1..1..1..1..1...-1.-1.-1.-1..1..1..1

..1..1..1..1..1..1..1...-1.-1.-1..1..1..1..1...-1.-1.-1.-1..1..1..1

CROSSREFS

Sequence in context: A221698 A081931 A156293 * A043498 A108571 A247700

Adjacent sequences:  A225305 A225306 A225307 * A225309 A225310 A225311

KEYWORD

nonn

AUTHOR

R. H. Hardin May 05 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 May 21 18:43 EDT 2019. Contains 323444 sequences. (Running on oeis4.)