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A141224 Maximum number of points visible from some point in a square n X n lattice. 6
1, 4, 9, 13, 19, 25, 35, 43, 55, 65, 81, 91, 111, 125, 147, 163, 187, 203, 233, 251, 283, 305, 337, 359, 399, 422, 465, 491, 531, 553, 609, 636, 691, 721, 769, 799, 863, 896, 961, 993, 1051, 1085, 1159, 1199, 1267, 1313, 1377, 1416, 1501, 1547, 1627, 1679 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Two points (a,b) and (c,d) are visible to each other when gcd(c-a,d-b)=1. Sequence A141225 gives the number of lattice points that have maximal visibility.

LINKS

T. D. Noe, Table of n, a(n) for n=1..1000

Eric Weisstein, MathWorld: Visible Point

FORMULA

The maximum number of visible points is slightly more than c*n^2, with c = 6/Pi^2.

MATHEMATICA

Table[mx=0; Do[cnt=0; Do[If[GCD[c-a, d-b]<2, cnt++ ], {a, n}, {b, n}]; If[cnt>mx, mx=cnt], {c, n}, {d, n}]; mx, {n, 20}]

CROSSREFS

Sequence in context: A184871 A184912 A035104 * A064423 A240692 A022130

Adjacent sequences:  A141221 A141222 A141223 * A141225 A141226 A141227

KEYWORD

nice,nonn

AUTHOR

T. D. Noe, Jun 15 2008

STATUS

approved

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Last modified July 23 08:53 EDT 2017. Contains 289686 sequences.