A274641 Counterclockwise square spiral constructed by greedy algorithm, so that each row, column, and diagonal contains distinct numbers. Start with 0 (so in this version a(n) = A274640(n) - 1).
0, 1, 2, 3, 1, 2, 3, 4, 5, 0, 3, 5, 1, 0, 5, 4, 2, 0, 4, 1, 5, 0, 1, 3, 4, 2, 6, 7, 4, 3, 8, 6, 7, 2, 9, 10, 3, 6, 7, 5, 2, 8, 4, 6, 7, 8, 9, 10, 11, 5, 7, 8, 10, 9, 11, 12, 6, 5, 9, 8, 11, 12, 13, 14, 7, 1, 8, 11, 6, 9, 10, 12, 13, 9, 8, 5, 12, 4, 2, 14, 15, 6, 0, 9, 12, 11, 13, 10, 14, 2, 7, 4, 0, 11, 10, 13, 6, 3, 1, 15, 8, 16, 0, 7, 10
Offset: 0
Keywords
Examples
From _Jon E. Schoenfield_, Dec 26 2016: (Start) The spiral begins: . 8--15---1---3---6--13--10--11---0---4---7 | | 16 7--14--13--12--11---8---9---5---6 2 | | | | 0 1 3--10---9---2---7---6---8 12 14 | | | | | | 7 8 6 2---4---5---0---1 3 11 10 | | | | | | | | 10 11 7 0 1---3---2 5 4 9 13 | | | | | | | | | | 14 6 5 4 2 0---1 3 7 10 11 | | | | | | | | | 13 9 2 1 3---4---5---0 6 8 12 | | | | | | | 6 10 8 5---0---1---3---4---2 7 9 | | | | | 3 12 4---6---7---8---9--10--11---5 0 | | | 11 13---9---8---5--12---4---2--14--15---6 | 9--14---0--11--15---7--13--12--10--17--16 . (End)
Links
- N. J. A. Sloane, Table of n, a(n) for n = 0..20000 [Based on Alois Heinz's b-file for A274640]
- F. Michel Dekking, Jeffrey Shallit, and N. J. A. Sloane, Queens in exile: non-attacking queens on infinite chess boards, Electronic J. Combin., 27:1 (2020), #P1.52.
- Rémy Sigrist, Colored representation of the spiral for -500 <= x, y <= 500
- N. J. A. Sloane, Confessions of a Sequence Addict (AofA2017), slides of invited talk given at AofA 2017, Jun 19 2017, Princeton. Mentions this sequence.
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