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 1-5 of 5 results.

A052408 Number of hyperbolic knots with n crossings (A002863 - A051764 - A051765).

Original entry on oeis.org

0, 0, 0, 1, 1, 3, 6, 20, 48, 164, 551, 2176, 9985, 46969, 253285, 1388694, 8053363, 48266380, 294130212
Offset: 1

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Keywords

Crossrefs

Cf. A052407.

Extensions

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

A052407 Number of nonhyperbolic prime knots with n crossings (A051764+A051765).

Original entry on oeis.org

0, 0, 1, 0, 1, 0, 1, 1, 1, 1, 1, 0, 3, 3, 8, 11
Offset: 1

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Keywords

Crossrefs

Cf. A052408.

A123192 Triangle read by rows: row n gives the coefficients in the expansion of x^abs(3*n - 2)*p(n;x), where p(n;x) denotes the bracket polynomial for the (2,n)-torus knots.

Original entry on oeis.org

-1, 0, 0, 0, -1, 0, 0, 0, 0, -1, -1, 0, 0, 0, 0, 0, 0, 0, -1, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, -1, 1, 0, 0, 0, -1, 0, 0, 0, 1, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 0, -1, -1, 0, 0, 0, 1, 0, 0, 0, -1, 0, 0, 0
Offset: 0

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Author

Roger L. Bagula, Oct 03 2006

Keywords

Comments

From Franck Maminirina Ramaharo, Aug 11 2018: (Start)
Using Kauffman's notation, the formal expression of the bracket polynomial for the (2,n)-torus knot is defined as follows:
K(n;A,B,d) = A*K(n-1;A,B,d) + B*(A + B*d)^(n - 1) with K(0;A,B,d) = d.
- The polynomial in this sequence is defined as p(n;x) = K(n;x,1/x,-x^2-x^(-2)), and verifies p(n;x) = x*p(n-1;x) + (-1)^(n - 1)*x^(-3*n + 2).
- The polynomial x*K(n;1,1,x) yields (x + 1)^n + x^2 - 1 which is the bracket evaluated at the shadow diagram of the (2,n)-torus knot, see A300453.
- The polynomial sqrt(x)*K(n;-1,sqrt(x),sqrt(x)) yields (x - 1)^n + (x - 1)*(-1)^n. This is the chromatic polynomial for the n-cycle graph which is the medial graph of the (2,n)-torus knot, see A137396.
The planar diagram of the (2,0)-torus knot is two non-intersecting circles.
(End)

Examples

			From _Franck Maminirina Ramaharo_, Aug 11 2018: (Start)
The bracket polynomial for some value of n:
  p(0;x) = -x^2 - 1/x^2;
  p(1;x) = -x^3;
  p(2;x) = -x^4 - 1/x^4;
  p(3;x) = -x^5 - 1/x^3 + 1/x^7;
  p(4;x) = -x^6 - 1/x^2 + 1/x^6 - 1/x^10;
  p(5;x) = -x^7 - 1/x   + 1/x^5 - 1/x^9  + 1/x^13;
  p(6;x) = -x^8 - 1     + 1/x^4 - 1/x^8  + 1/x^12 - 1/x^16;
  p(7;x) = -x^9 - x     + 1/x^3 - 1/x^7  + 1/x^11 - 1/x^15 + 1/x^19;
  ...
The triangle giving the coefficients in x^abs(3*n - 2)*p(n;x) begins:
  -1, 0, 0, 0, -1
   0, 0, 0, 0, -1
  -1, 0, 0, 0,  0, 0, 0, 0, -1
   1, 0, 0, 0, -1, 0, 0, 0,  0, 0, 0, 0, -1
  -1, 0, 0, 0,  1, 0, 0, 0, -1, 0, 0, 0,  0, 0, 0, 0, -1
   1, 0, 0, 0, -1, 0, 0, 0,  1, 0, 0, 0, -1, 0, 0, 0,  0, 0, 0, 0, -1
  ...
(End)
		

References

  • Louis H. Kauffman, Knots and Physics (Third Edition), World Scientific, 2001. See p. 38 and p. 353.

Crossrefs

Programs

  • Maxima
    K(n, A, B, d) := if n = 0 then d else A*K(n - 1, A, B, d) + B*(A + B*d)^(n - 1)$
    p(n, x) := x^abs(3*n - 2)*K(n, x, 1/x, -x^(-2) - x^2)$
    t(n, k) := ratcoef(p(n, x), x, k)$
    T:[]$
    for n:0 thru 10 do T:append(T, makelist(t(n,k), k, 0, max(4, 4*n)))$
    T; /* Franck Maminirina Ramaharo, Aug 11 2018 */

Extensions

Partially edited by N. J. A. Sloane, May 22 2007
Edited, new name, and corrected by Franck Maminirina Ramaharo, Aug 11 2018

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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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

A379242 Minimum crossing number at which there are n torus knots.

Original entry on oeis.org

1, 3, 15, 63, 189, 432, 792, 1232, 1584, 2880, 4320, 5040, 6336, 7920, 12096, 15120, 19008, 22176, 30240, 33264, 43200, 47520, 44352, 65520, 75600, 108000, 90720, 120960, 168480, 131040, 151200, 181440, 252000, 196560, 221760, 237600, 362880, 403200, 302400
Offset: 0

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Author

Alex Klotz, Dec 18 2024

Keywords

Comments

Minimum number that can be factored N different ways into p*(q-1) for coprime p and q with p>q. e.g. 63=63*(2-1)=9*(8-1)=21*(4-1); 63 is the smallest crossing number with three torus knots. Odd numbers will admit an alternating (p,2) torus knot with p crossings, all others with q>2 are non-alternating. Based on definition of torus knot and data from A051764.

Examples

			3 = 3*(2-1), 15 = 15*(2-1) = 5*(4-1), 63 = 63*(2-1) = 9*(8-1) = 21*(4-1).
		

Crossrefs

First occurrence of each n in A051764.

Extensions

More terms from Alois P. Heinz, Dec 29 2024
Showing 1-5 of 5 results.