A300154 Consider a spiral on an infinite hexagonal grid. a(n) is the number of cells in the part of the spiral from 1st to n-th cell that are on the same column or diagonal (in any of three directions) as the n-th cell along the spiral, including that cell itself.
1, 2, 3, 3, 4, 4, 5, 5, 5, 6, 6, 7, 6, 7, 7, 8, 7, 8, 9, 8, 9, 8, 9, 10, 9, 10, 11, 9, 10, 11, 10, 11, 12, 10, 11, 12, 13, 11, 12, 13, 11, 12, 13, 14, 12, 13, 14, 15, 12, 13, 14, 15, 13, 14, 15, 16, 13, 14, 15, 16, 17, 14
Offset: 1
Examples
a(3) = 3 because the third hexagon is on the same diagonal as itself, the second hexagon, and the original hexagon. a(7) = 5 because the 7th cell is on the same columns/diagonals as cells No. 2 (in one direction), 6 (in another direction), 1 and 4 (in the third direction), plus itself.
Links
- Peter Kagey, Table of n, a(n) for n = 1..5000
- Code Golf Stack Exchange, What can you see on a hexagonal spiral?
- Emily Chitwood, Example of cell sight
- Emily Chitwood, Example of spiral path
- Emily Chitwood, Example of initial terms
- Peter Kagey, An animated illustration of the first fifteen terms.
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