A141249 -id:A141249 - cp's OEIS frontend

A141248 Number of points having minimal visibility in a square n X n lattice of points.

1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 36, 1, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 9, 4, 4, 52, 4, 4, 8, 4, 4, 44, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 12, 4, 4, 4, 4, 1, 4, 4, 4, 4, 4, 4, 4, 1, 4, 4, 4, 20, 4, 4, 4, 4, 8, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4

Offset: 1

T. D. Noe, Jun 17 2008

nonn

Sequence A141247 gives the minimum number of points visible from a point. By symmetry, when a(n) is odd, the central point in the lattice can see only the minimal number of points. When a(n)=1, the central point is the only such point. See A141249 for the n X n lattices that have such a central point.

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

Cf. A141225.

Table[mn=n^2+1; pts=0; Do[cnt=0; Do[If[GCD[c-a,d-b]<2, cnt++ ], {a,n}, {b,n}]; If[cnt

A141250 Prime powers related to minimal visibility in the square n X n lattice.

Original entry on oeis.org

11, 17, 23, 37, 41, 97, 101, 121, 137, 157, 191, 211, 223, 227, 331, 347, 431, 443, 457

Offset: 1

T. D. Noe, Jun 17 2008

nonn

So far 121 is the only composite here. The numbers in A141249 greater than 1 are 2*a(n)-1.

Cf. A141246.

cp's OEIS Frontend

A141248 Number of points having minimal visibility in a square n X n lattice of points.

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