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!)
A237530 Number of non-equivalent (mod D_3) ways to choose three points in an n X n X n triangular grid so that they do not form a 2 X 2 X 2 subtriangle. 1
0, 4, 22, 82, 231, 566, 1216, 2410, 4428, 7712, 12780, 20392, 31409, 47032, 68594, 97878, 136836, 187998, 254100, 338602, 445213, 578524, 743424, 945860, 1192126, 1489768, 1846734, 2272430, 2776725, 3371170, 4067840, 4880734, 5824442, 6915732, 8172036, 9613236 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

COMMENTS

Without the restriction "non-equivalent (mod D_3)" the numbers are given by A234250.

LINKS

Heinrich Ludwig, Table of n, a(n) for n = 2..1000

Index entries for linear recurrences with constant coefficients, signature (3,0,-7,3,6,0,-6,-3,7,0,-3,1)

FORMULA

a(n) = (n^6 + 3*n^5 - 3*n^4 + 10*n^3 - 48*n^2 + IF(n==1 mod 2)*(27*n^2 - 45*n - 9) + IF(n==1 mod 3)*64)/288.

G.f.: x^3*(x^7-x^6-2*x^5-15*x^4-13*x^3-16*x^2-10*x-4) / ((x-1)^7*(x+1)^3*(x^2+x+1)). - Colin Barker, Feb 14 2014

CROSSREFS

Cf. A234250, A234247.

Sequence in context: A201127 A259709 A078155 * A096167 A060453 A038382

Adjacent sequences:  A237527 A237528 A237529 * A237531 A237532 A237533

KEYWORD

nonn,easy

AUTHOR

Heinrich Ludwig, Feb 13 2014

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 September 28 02:07 EDT 2020. Contains 337392 sequences. (Running on oeis4.)