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  "body": "\n## Summary\n\nThe crossing number of a [[knot|QYEAZTYGPT]] is the least number of crossings in any diagram of the knot.\nIt is a [[knot invariant|GZQ5ZE3X6G]] with values in the natural numbers, and knot tables list knots by their crossing number.\nIt is easy to define but hard to compute, because one must rule out all diagrams with fewer crossings.\n\n## Explanations\n\n### L1 human\n\nDraw a knot on paper, with a gap wherever one strand passes under another.\nDifferent drawings of the same knot can have different numbers of crossings.\nThe crossing number is the smallest number that any drawing can achieve.\nThe unknot has crossing number $0$, the [[trefoil|VYTYSVHN4A]] has $3$, and the [[figure-eight knot|C01XBGAHC6]] has $4$.\n",
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