login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A214385 Number of 3 X 3 X 3 triangular 0..n arrays with no element lying outside the (possibly reversed) range delimited by its sw and se neighbors, and no element equal to its horizontal neighbors. 1
8, 94, 456, 1506, 3976, 9044, 18480, 34812, 61512, 103202, 165880, 257166, 386568, 565768, 808928, 1133016, 1558152, 2107974, 2810024, 3696154, 4802952, 6172188, 7851280, 9893780, 12359880, 15316938, 18840024, 23012486, 27926536, 33683856 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Row 3 of A214384.

LINKS

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

FORMULA

Empirical: a(n) = (1/36)*n^6 + (7/15)*n^5 + (22/9)*n^4 + (25/6)*n^3 + (55/36)*n^2 - (19/30)*n.

Conjectures from Colin Barker, Jul 22 2018: (Start)

G.f.: 2*x*(4 + 19*x - 17*x^2 + 4*x^3) / (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=3:

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

...2.1....3.0....0.2....3.1....2.3....0.1....2.1....2.0....0.2....3.0....1.2

..3.0.3..3.0.1..0.2.0..3.1.2..3.0.3..2.0.3..3.2.0..2.3.0..1.0.2..3.1.0..1.3.2

CROSSREFS

Cf. A214384.

Sequence in context: A299034 A299339 A299846 * A121161 A098269 A010565

Adjacent sequences:  A214382 A214383 A214384 * A214386 A214387 A214388

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 14 2012

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 3 17:49 EDT 2022. Contains 357237 sequences. (Running on oeis4.)