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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 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: A301705 A309456 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 May 27 16:47 EDT 2020. Contains 334664 sequences. (Running on oeis4.)