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 A295771 a(n) is the minimum size of a planar additive basis for the square [0,n]^2. 2
 1, 3, 4, 7, 8, 11, 12, 14, 16, 19, 20, 23, 24, 26 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS A planar additive basis is a set of points with nonnegative integer coordinates such that their pairwise sums cover a given rectangle of points with integer coordinates. Pairwise sums of a point with itself are included. a(n) <= 2n+1, because there is an L-shaped basis of that size. a(n) <= 2n if n is even and nonzero, because of a square-shaped "boundary basis" with sides at coordinates 0 and n/2. LINKS J. Kohonen, V. Koivunen and R. RajamÃ¤ki, Planar additive bases for rectangles, Journal of Integer Sequences, 21 (2018), Article 18.9.8. EXAMPLE a(3)=7: The square [0,3]^2 is covered by the pairwise sums of the L-shaped basis {(0,0),(1,0),(2,0),(3,0),(0,1),(0,2),(0,3)}, which has 7 elements. CROSSREFS A295774 is the restricted version. A001212 concerns the one-dimensional problem. Main diagonal of A306608. Sequence in context: A070874 A187582 A288553 * A285503 A327221 A014601 Adjacent sequences:  A295768 A295769 A295770 * A295772 A295773 A295774 KEYWORD nonn,more AUTHOR Jukka Kohonen, Nov 27 2017 EXTENSIONS a(12), a(13) from Jukka Kohonen, Dec 17 2018 STATUS approved

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Last modified October 16 18:03 EDT 2019. Contains 328102 sequences. (Running on oeis4.)