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A141249 Numbers n such that the central point of the square n X n lattice sees the minimal number of points. 2
1, 21, 33, 45, 73, 81, 193, 201, 241, 273, 313, 381, 421, 445, 453, 661, 693, 861, 885, 913 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

These n are the numbers for which A141248(n) is odd. Note that n must be odd. When A141248(n)=1, the central point is the only point seeing the minimal number of points. These numbers are 1 or 9 (mod 12). These numbers also seem to produce cubic n X n X n lattices in which the central point has minimal visibility. Note that for n>1, n+1 is twice a prime power in A141250.

LINKS

Table of n, a(n) for n=1..20.

CROSSREFS

Cf. A141226.

Sequence in context: A119973 A279229 A339963 * A026068 A217263 A330441

Adjacent sequences:  A141246 A141247 A141248 * A141250 A141251 A141252

KEYWORD

nonn

AUTHOR

T. D. Noe, Jun 17 2008

STATUS

approved

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Last modified June 22 14:32 EDT 2021. Contains 345380 sequences. (Running on oeis4.)