cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

Showing 1-9 of 9 results.

A002863 Number of prime knots with n crossings.

Original entry on oeis.org

0, 0, 1, 1, 2, 3, 7, 21, 49, 165, 552, 2176, 9988, 46972, 253293, 1388705, 8053393, 48266466, 294130458
Offset: 1

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Author

Keywords

Comments

Prime knot: a nontrivial knot which cannot (as a composite knot can) be written as the knot sum of two nontrivial knots. - Jonathan Vos Post, Apr 30 2011

References

  • For convenience, many references and links related to the enumeration of knots are collected here, even if they do not explicitly refer to this sequence.
  • C. C. Adams, The Knot Book, Freeman, NY, 2001; see p. 33.
  • C. Cerf, Atlas of oriented knots and links, Topology Atlas 3 no. 2 (1998).
  • Peter R. Cromwell, Knots and Links, Cambridge University Press, 2004, pp. 209-211.
  • Martin Gardner, The Last Recreations, Copernicus, 1997, 67-84.
  • N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
  • P. G. Tait, Scientific Papers, Cambridge Univ. Press, Vol. 1, 1898, Vol. 2, 1900, see Vol. 1, p. 345.
  • M. B. Thistlethwaite, personal communication.

Crossrefs

Formula

a(n) = A051766(n) + A051769(n) + A051767(n) + A051768(n) + A052400(n). - Andrew Howroyd, Oct 15 2020

Extensions

This is stated incorrectly in CRC Standard Mathematical Tables and Formulae, 30th ed., first printing, 1996, p. 320.
Terms from Hoste et al. added by Eric W. Weisstein
Consolidated references and links on enumeration of knots into this entry, also created entry for knots in Index to OEIS. - N. J. A. Sloane, Aug 25 2015
a(17)-a(19) computed by Benjamin Burton, added by Alex Klotz, Jun 21 2021
a(17)-a(19) computed by Benjamin Burton corrected by Andrey Zabolotskiy, Nov 25 2021

A018240 Number of rational knots (or two-bridge knots) with n crossings (up to mirroring).

Original entry on oeis.org

1, 1, 2, 3, 7, 12, 24, 45, 91, 176, 352, 693, 1387, 2752, 5504, 10965, 21931, 43776, 87552, 174933, 349867, 699392, 1398784, 2796885, 5593771, 11186176, 22372352, 44741973, 89483947, 178962432, 357924864, 715838805, 1431677611, 2863333376, 5726666752
Offset: 3

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Author

Alexander Stoimenow (stoimeno(AT)math.toronto.edu)

Keywords

Examples

			The a(7)=7 rational knots with 7 crossings are 7, 52, 43, 322, 313, 2212, 21112. All the rational knots are listed in A122495.
		

References

  • S. Jablan and R. Sazdanović, LinKnot: Knot Theory by Computer, World Scientific Press, 2007.

Crossrefs

Cf. A018240 = number of rational knots, A005418 = number of rational knots and links, A001045 = Jacobsthal sequence (the difference between the number of rational links and knots), A090597 = rational links with n crossings, A329908, A336398.

Programs

  • Mathematica
    LinearRecurrence[{-1, 5, 5, -2, -2, -8, -8}, {1, 1, 2, 3, 7, 12, 24}, 50] (* Harvey P. Dale, Sep 03 2013 *)
    CoefficientList[Series[(1 - 2 x^2 - x^3 - x^4)/((1 - 2 x) (1 + x) (1 - 2 x^2) (1 + x^2)), {x, 0, 50}], x] (* Vincenzo Librandi, Aug 07 2014 *)
  • PARI
    Vec((1-2*x^2-x^3-x^4)*x^3/((1-2*x)*(1+x)*(1-2*x^2)*(1+x^2))+O(x^66)) \\ Joerg Arndt, Aug 07 2014

Formula

a(n) = - a(n-1) + 5*(a(n-2)+a(n-3)) - 2*(a(n-4)+a(n-5)) - 8*(a(n-6)+a(n-7)). [Originally contributed as a separate sequence entry by Thomas A. Gittings, Dec 11 2003; see Stoimenow, Corollary 5.1 for proof]
G.f.: (1-2*x^2-x^3-x^4)*x^3/((1-2*x)*(1+x)*(1-2*x^2)*(1+x^2)). - R. J. Mathar, Sep 08 2008

Extensions

Edited by Andrey Zabolotskiy, Jun 18 2020

A051765 Number of prime satellite knots with n crossings.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 6, 10, 29, 86, 245
Offset: 1

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Author

Keywords

Comments

Weisstein says that Hoste et al. said that all satellite knots are prime, but actually they didn't say it about all satellite knots; moreover, the conventional definition of satellite knots implies that all composite knots are satellite. - Andrey Zabolotskiy, Nov 25 2021

Crossrefs

Extensions

a(17)-a(19) from Burton's data added by Andrey Zabolotskiy, Nov 25 2021

A086826 Number of nonsplittable links (prime or composite) with n crossings.

Original entry on oeis.org

1, 0, 1, 1, 3, 4, 15, 24, 82
Offset: 0

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Author

Steven Finch, Aug 07 2003

Keywords

Comments

A link L is splittable if we can embed a plane in R^3, disjoint from L, that separates one or more components of L from other components of L. Otherwise L is nonsplittable.

Examples

			a(5)=4 since we have 2 prime knots, as well as the Whitehead link; and the trefoil knot linked with a circle.
a(6)=15 since we have 3 prime knots, as well as 2 composite knots (the square & granny knots); 6 prime links; a chain of four circles simply-intertwined; four circles simply-intertwined in the shape of a "T"; three circles, two doubly-intertwined and two simply-intertwined; and the figure-eight knot linked with a circle.
		

Crossrefs

Extensions

a(7) and a(8) from Stéphane Legendre, Jan 06 2014

A283314 Total number of knots (prime or composite) with <= n crossings.

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 10, 18, 44
Offset: 0

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Author

N. J. A. Sloane, Mar 08 2017, following a suggestion from Daniel Forgues

Keywords

Crossrefs

Partial sums of A086825.
Cf. A283315.

Extensions

a(8) corrected from A086825 by Kyle Miller, Oct 14 2020

A277740 Knot diagrams with n crossings.

Original entry on oeis.org

1, 2, 6, 36, 276, 2936, 35872, 484088, 6967942, 105555336, 1664142836
Offset: 0

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Author

N. J. A. Sloane, Nov 07 2016

Keywords

Comments

From Andrey Zabolotskiy, Dec 24 2018: (Start)
It follows from Definition 7 of the paper by Cantarella, Chapman & Mastin that every one of A008988(n) knot shadows contributes some diagrams to a(n). The number of diagrams contributed is shown near knot shadows in the illustration linked below (e.g., the knot shadow looking like an n-gon with petals contributes A000031(n) inequivalent diagrams, while non-symmetric knot shadows contribute 2^n diagrams each). Note that the orientation of knot shadows is not shown when it is not needed to distinguish two knot shadows, but all the knot shadows are oriented, which spoils the symmetry of many of them. (Even though the paper itself starts from unoriented knot shadows counted by A008989, eventually the orientation is assigned to the diagrams.)
The more symmetric a knot shadow is, the fewer inequivalent diagrams it contributes. The knot shadows and the diagrams generated by them are oriented but immersed into unoriented spheres. When determining equivalent diagrams, they can be rotated on the sphere and turned "inside out" but not reflected. Some planar drawings of knot shadows make them look less symmetric than they actually are (taking into account their immersion into the sphere).
Note that this equivalence relation distinguishes many more knot diagrams than the ambient isotopy of knots, cf. A086825. (End)

Crossrefs

Extensions

a(0)-a(2) from Andrey Zabolotskiy, Dec 24 2018

A283315 Total number of nontrivial knots (prime or composite) with <= n crossings.

Original entry on oeis.org

0, 0, 0, 1, 2, 4, 9, 17, 43
Offset: 0

Views

Author

N. J. A. Sloane, Mar 08 2017, following a suggestion from Daniel Forgues

Keywords

Crossrefs

Equals A283314(n) - 1.

Extensions

a(8) corrected from A086825 by Kyle Miller, Oct 14 2020

A116584 Number of prime knots with <= n crossings.

Original entry on oeis.org

0, 0, 1, 2, 4, 7, 14, 35, 84, 249, 801, 2977, 12965, 59937, 313230, 1701935, 9755328, 58021794, 352152252
Offset: 1

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Author

Jonathan Vos Post, May 09 2006

Keywords

Crossrefs

Partial sums of A002863.

Extensions

a(17)-a(19) added from the data at A002863 by Amiram Eldar, Jul 22 2025

A375605 Number of composite knots with n crossings.

Original entry on oeis.org

0, 0, 0, 0, 0, 0, 2, 1, 5
Offset: 0

Views

Author

Jens Ahlström, Aug 20 2024

Keywords

Comments

A knot is composite if and only if it can be written as the knot sum of two nontrivial knots.

Examples

			For n = 6 there are totally 5 knots out of which 3 are prime, so a(6) = 5 - 3 = 2.
		

Crossrefs

Formula

a(n) = A086825(n) - A002863(n), for all n > 0.
Showing 1-9 of 9 results.