%I A141224
%S A141224 1,4,9,13,19,25,35,43,55,65,81,91,111,125,147,163,187,203,233,251,283,
%T A141224 305,337,359,399,422,465,491,531,553,609,636,691,721,769,799,863,896,
%U A141224 961,993,1051,1085,1159,1199,1267,1313,1377,1416,1501,1547,1627,1679
%N A141224 Maximum number of points visible from some point in a square n x n lattice.
%C A141224 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.
%H A141224 T. D. Noe, <a href="b141224.txt">Table of n, a(n) for n=1..1000</a>
%H A141224 Eric Weisstein, <a href="http://mathworld.wolfram.com/VisiblePoint.html">
               MathWorld: Visible Point</a>
%F A141224 The maximum number of visible points is slightly more than c*n^2, with 
               c = 6/pi^2.
%t A141224 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}]
%Y A141224 Sequence in context: A093410 A090498 A035104 this_sequence A064423 A022130 
               A042125
%Y A141224 Adjacent sequences: A141221 A141222 A141223 this_sequence A141225 A141226 
               A141227
%K A141224 nice,nonn
%O A141224 1,2
%A A141224 T. D. Noe (noe(AT)sspectra.com), Jun 15 2008