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A240442 Number of ways to place 5 points on a triangular grid of side n so that no three of these points are vertices of an equilateral triangle of any orientation. 4
0, 39, 1194, 11259, 64776, 275805, 957516, 2859768, 7606821, 18444537, 41458599, 87464157, 174846963, 333687378, 611613150, 1081890447 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,2

LINKS

Table of n, a(n) for n=3..18.

FORMULA

a(n) = (n^10 + 5*n^9 - 30*n^8 - 150*n^7)/3840 + O(n^6).

CROSSREFS

Cf. A240439, A240440, A240441.

Sequence in context: A251327 A014936 A227524 * A009729 A078970 A020303

Adjacent sequences:  A240439 A240440 A240441 * A240443 A240444 A240445

KEYWORD

nonn,more

AUTHOR

Heinrich Ludwig, Apr 08 2014

EXTENSIONS

a(16)-a(18) from Heinrich Ludwig, Apr 25 2014

STATUS

approved

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Last modified March 25 15:02 EDT 2019. Contains 321470 sequences. (Running on oeis4.)