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 A141225 Number of points having maximal visibility in a square n x n lattice. 5
 1, 4, 1, 4, 8, 16, 8, 12, 16, 36, 9, 60, 16, 16, 8, 12, 12, 12, 12, 36, 16, 16, 25, 4, 16, 8, 5, 12, 24, 64, 12, 8, 4, 4, 25, 16, 4, 8, 1, 20, 16, 4, 20, 12, 4, 4, 9, 8, 4, 4, 4, 4, 12, 4, 4, 4, 4, 12, 9, 4, 8, 4, 8, 12, 8, 4, 4, 8, 4, 16, 12, 20, 4, 8, 4, 4, 16, 4, 4, 4, 4, 4, 4, 4, 4, 4, 8, 4, 4 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Sequence A141224 gives the maximum number of points visible from some point. By symmetry, when a(n) is odd, the central point in the lattice can see the maximal number of points. When a(n)=1, the central point is the only such point. See A141226 for the n x n lattices that have such a central point. LINKS T. D. Noe, Table of n, a(n) for n=1..1000 MATHEMATICA Table[mx=0; pts=0; Do[cnt=0; Do[If[GCD[c-a, d-b]<2, cnt++ ], {a, n}, {b, n}]; If[cnt>mx, mx=cnt; pts=1, If[cnt==mx, pts++ ]], {c, n}, {d, n}]; pts, {n, 20}] CROSSREFS Sequence in context: A244097 A162956 A131112 * A344947 A079185 A133819 Adjacent sequences:  A141222 A141223 A141224 * A141226 A141227 A141228 KEYWORD nonn AUTHOR T. D. Noe, Jun 15 2008 STATUS approved

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Last modified June 23 08:25 EDT 2021. Contains 345395 sequences. (Running on oeis4.)