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%I #7 Jun 13 2014 12:06:30
%S 0,11,266,2344,12907,53307,180876,530654,1391647,3335627,7426885,
%T 15544434,30867669,58574800,106838511,188190111,321383808,533857914
%N 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.
%F a(n) = (n^10 + 5*n^9 - 10*n^8 - 195*n^7)/23040 + O(n^6)
%Y Cf. A243207, A243214, A001399, A227327, A243208, A243209.
%K nonn,more
%O 3,2
%A _Heinrich Ludwig_, Jun 10 2014