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A090936 Number of rational knots and links with n crossings with unknotting (unlinking) gap. 2
1, 1, 5, 5, 23, 36, 106, 180 (list; graph; refs; listen; history; text; internal format)
OFFSET

9,3

REFERENCES

S. A. Bleiler, A note on unknotting number, Math. Proc. Camb. Phil. Soc. 96 (1984) 469-471.

D. Garity, Unknotting numbers are not realized in minimal projections for a class of rational knots. Proceedings of the "II Italian-Spanish Congress on General Topology and its Applications" (Trieste, 1999). Rend. Istit. Mat. Univ. Trieste 32 (2001), suppl. 2, 59-72 (2002).

Y. Nakanishi, Unknotting numbers and knot diagrams with the minimum crossings, Math. Sem. Notes Kobe Univ. 11 (1983) 257-258.

LINKS

Table of n, a(n) for n=9..16.

D. Garity, Unknotting Numbers are not Realized in Minimal Projections for a Class of Rational Knots

S. Jablan and R. Sazdanovic, LinKnot

EXAMPLE

The first link with unlinking gap is 9_4^2=414.

For n=11 there are links 434,614,5132,51113, etc.

CROSSREFS

Cf. A090935.

Sequence in context: A255456 A338936 A175713 * A262117 A145764 A165826

Adjacent sequences:  A090933 A090934 A090935 * A090937 A090938 A090939

KEYWORD

nonn

AUTHOR

Slavik Jablan and Radmila Sazdanovic (jablans(AT)mi.sanu.ac.rs), Feb 26 2004; corrected Aug 29 2004

STATUS

approved

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Last modified January 17 22:33 EST 2022. Contains 350410 sequences. (Running on oeis4.)