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A339756 Mark each point on the n X n X n grid with the number of points that are visible from it; a(n) is the number of distinct values in the grid.

%I A339756 #40 Feb 19 2021 20:35:04
%S A339756 1,4,4,8,4,17,12,15,14,33,12,58,28,43,52,113,39,140,57,124,129,240,66,
%T A339756 241,173,270,217,362,58,388,292,454,351,539,166,783,471,723,463,880,
%U A339756 229,1134,642,843,763,1441,311,1415,740,1295,987,1888,357,1629,1063,1750,1231,2381,289,2652
%N A339756 Mark each point on the n X n X n grid with the number of points that are visible from it; a(n) is the number of distinct values in the grid.
%C A339756 a(n) <= A058187(n). This is because A058187(n) is the maximum number of points required to calculate a(n).
%H A339756 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/VisiblePoint.html">Visible Point</a>
%e A339756 a(1) = 1 because there are 7 visible points from every point on the grid.
%e A339756 a(2) = 4 because 19 points are visible from every vertex of the grid, 23 points are visible from the midpoint of every edge of the grid, 25 points are visible from the midpoint of every face of the grid, and 26 points are visible from the middle of the grid.
%e A339756 a(3) = 4 because 49 points are visible from every vertex of the grid, 53 points are visible from the inner points of every edge of the grid, 55 points are visible from the inner points of every face of the grid, and 56 points are visible from the inner points of the grid.
%o A339756 (PARI) \\ n = side length, d = dimension
%o A339756 cdvps(n, d) ={my(m=Map());
%o A339756   forvec(u=vector(d, i, [0, n\2]),
%o A339756     my(c=0); forvec(v=[[t-n, t]|t<-u], c+=(gcd(v)==1));
%o A339756     mapput(m, c, 1), 1);
%o A339756   #m; }
%o A339756 a(n) = cdvps(n, 3)
%Y A339756 Cf. A049687, A049691, A058187, A090025, A339400.
%K A339756 nonn
%O A339756 1,2
%A A339756 _Torlach Rush_, Dec 15 2020