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A292276 a(n) = number of vertices of the convex hull of the set of points of norm <= n^2 in square lattice. 1
1, 4, 4, 8, 12, 12, 12, 12, 20, 12, 20, 20, 20, 20, 20, 20, 20, 24, 28, 20, 20, 20, 36, 36, 28, 20, 36, 36, 36, 36, 28, 36, 36, 36, 44, 36, 36, 36, 36, 52, 44, 36, 36, 36, 52, 44, 52, 52, 44, 52, 44, 60, 52, 44, 52, 44, 52, 52, 52, 52, 60, 52, 52, 52, 68, 44 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

The convex hull of a finite point set in dimension 2, say S, forms a convex polygon whose vertices are in S.

For any n >= 0, A000328(n) gives the number of elements of the set of points of norm <= n^2 in square lattice.

For symmetry reasons, a(n) is a multiple of 4 for any n > 0.

LINKS

Table of n, a(n) for n=0..65.

Rémy Sigrist, C++ program for A292276

Rémy Sigrist, Illustration of the convex hulls for n=0..10

Wikipedia, Convex hull of a finite point set

EXAMPLE

See Links section.

PROG

(C++) See Links section.

CROSSREFS

Cf. A000328, A046109.

Sequence in context: A152967 A301705 A004024 * A278083 A086663 A003829

Adjacent sequences:  A292273 A292274 A292275 * A292277 A292278 A292279

KEYWORD

nonn

AUTHOR

Rémy Sigrist, Sep 13 2017

STATUS

approved

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Last modified March 26 10:18 EDT 2019. Contains 321491 sequences. (Running on oeis4.)