OFFSET
1,2
COMMENTS
Two points (a,b) and (c,d) are visible to each other when gcd(c-a,d-b)=1. Sequence A141248 gives the number of lattice points that have minimal visibility.
LINKS
T. D. Noe, Table of n, a(n) for n=1..1000
Eric Weisstein, MathWorld: Visible Point
FORMULA
The minimum number of visible points is slightly less than c*n^2, with c = 6/pi^2.
MATHEMATICA
Table[mn=n^2+1; Do[cnt=0; Do[If[GCD[c-a, d-b]<2, cnt++ ], {a, n}, {b, n}]; If[cnt<mn, mn=cnt], {c, n}, {d, n}]; mn, {n, 20}]
CROSSREFS
KEYWORD
nonn
AUTHOR
T. D. Noe, Jun 17 2008
STATUS
approved