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A243210 Number of inequivalent (mod D_3) ways to place 5 points on a triangular grid of side n so that no three of them are vertices of an equilateral triangle with sides parallel to the grid. 4
0, 11, 266, 2344, 12907, 53307, 180876, 530654, 1391647, 3335627, 7426885, 15544434, 30867669, 58574800, 106838511, 188190111, 321383808, 533857914 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Table of n, a(n) for n=3..20.

FORMULA

a(n) = (n^10 + 5*n^9 - 10*n^8 - 195*n^7)/23040 + O(n^6)

CROSSREFS

Cf. A243207, A243214, A001399, A227327, A243208, A243209.

Sequence in context: A130177 A100841 A003389 * A232695 A027019 A255955

Adjacent sequences:  A243207 A243208 A243209 * A243211 A243212 A243213

KEYWORD

nonn,more

AUTHOR

Heinrich Ludwig, Jun 10 2014

STATUS

approved

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Last modified September 26 15:47 EDT 2020. Contains 337373 sequences. (Running on oeis4.)