A243214 Number of 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.

0, 63, 1566, 13971, 77124, 319206, 1083723, 3181401, 8344854, 20006349, 44548227, 93248628, 185176866, 351410664, 640972980, 1129067352, 1928196432, 3203016813

Offset

3,2

Links

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

Formula

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

Crossrefs

Cf. A243211, A243210, A000217, A050534, A243212, A243213.

Sequence in context: A132465 A202983 A107319 * A341569 A005463 A160896

Adjacent sequences: A243211 A243212 A243213 * A243215 A243216 A243217

Keyword

nonn,more

Author

Heinrich Ludwig, Jun 10 2014

Status

approved