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 A160847 Number of lines through at least 2 points of a 7 X n grid of points. 2
 0, 1, 51, 100, 181, 274, 405, 536, 709, 894, 1111, 1330, 1591, 1858, 2167, 2482, 2825, 3180, 3577, 3974, 4413, 4860, 5339, 5824, 6351, 6884, 7455, 8032, 8641, 9262, 9925, 10584, 11285, 11998, 12743, 13494, 14283, 15078, 15915, 16758, 17633, 18516 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..1000 FORMULA a(n) = (1/2)*(f(m,n,1)-f(m,n,2)) where f(m,n,k) = Sum((n - |kx|)*(m - |ky|)); -n < kx 0, i, 0] p2[m_, n_, x_, y_]:=p2[m, n, x, y]=(n-x)*(m-y)-p[n-2*x]*p[m-2*y] p3[m_, n_, x_, y_]:=p2[m, n, x, y]-2*p2[m, n-1, x, y]+p2[m, n-2, x, y] p4[m_, n_]:=p4[m, n]=If[Mod[n, 2]==0, 0, p42[m, n]] p42[m_, n_]:=p42[m, n]=Sum[p43[m, n, y], {y, 1, m-1}] p43[m_, n_, y_]:=If[GCD[(n-1)/2, y]==1, p3[m, n, (n-1)/2, y], 0] Table[a[n], {n, 0, 41}] CROSSREFS Sequence in context: A229274 A044140 A044521 * A260517 A235878 A015705 Adjacent sequences:  A160844 A160845 A160846 * A160848 A160849 A160850 KEYWORD nonn AUTHOR Seppo Mustonen, May 28 2009 STATUS approved

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Last modified October 21 11:05 EDT 2019. Contains 328294 sequences. (Running on oeis4.)