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 1-10 of 22 results. Next

A060595 Number of tilings of the 3-dimensional zonotope constructed from D vectors.

Original entry on oeis.org

1, 2, 10, 148, 7686, 1681104, 1881850464, 13227777493060
Offset: 3

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Author

Matthieu Latapy (latapy(AT)liafa.jussieu.fr), Apr 12 2001

Keywords

Comments

The zonotope Z(D,d) is the projection of the D-dimensional hypercube onto the d-dimensional space and the tiles are the projections of the d-dimensional faces of the hypercube. Here d=3 and D varies.
Also the number of signotopes of rank 4, i.e., mappings X:{{1..n} choose 4}->{+,-} such that for any four indices a < b < c < d < e, the sequence X(a,b,c,d), X(a,b,c,e), X(a,b,d,e), X(a,c,d,e), X(b,c,d,e), changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Sep 13 2021

Examples

			Z(3,3) is simply a cube and the only possible tile is Z(3,3) itself, therefore the first term of the series is 1. It is well known that there are always two d-tilings of Z(d+1,d), therefore the second term is 2. More examples are available on my web page.
		

References

  • A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G.M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46, Second Edition, Cambridge University Press, 1999
  • V. Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.

Crossrefs

Cf. A006245 (two-dimensional tilings), A060596-A060602.
Column k=3 of A060637.

Formula

Asymptotics: a(n) = 2^(Theta(n^3)). This is Bachmann-Landau notation, that is, there are constants n_0, c, and d, such that for every n >= n_0 the inequality 2^{c n^3} <= a(n) <= 2^{d n^3} is satisfied. - Manfred Scheucher, Sep 22 2021

Extensions

a(8)-a(9) from Manfred Scheucher, Sep 13 2021
Edited by Manfred Scheucher, Mar 08 2022
a(10) from Manfred Scheucher, Jul 17 2023

A006248 Number of projective pseudo order types: simple arrangements of pseudo-lines in the projective plane.

Original entry on oeis.org

1, 1, 1, 1, 1, 4, 11, 135, 4382, 312356, 41848591, 10320613331
Offset: 1

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Author

Keywords

References

  • J. Bokowski, personal communication.
  • J. E. Goodman and J. O'Rourke, editors, Handbook of Discrete and Computational Geometry, CRC Press, 1997, p. 102.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A006245, A006246, A018242, A063666. A diagonal of A063851.

Formula

Asymptotics: 2^{Cn^2} <= a(n) <= 2^{Dn^2} for every n >= N, where N,C,D are constants with 0.1887Manfred Scheucher, Apr 10 2025 on personal communication with Günter Rote.]

Extensions

a(11) from Franz Aurenhammer (auren(AT)igi.tu-graz.ac.at), Feb 05 2002
a(12) from Manfred Scheucher and Günter Rote, Sep 07 2019
Definition corrected by Günter Rote, Dec 01 2021

A006247 Number of simple arrangements of n pseudolines in the projective plane with a marked cell. Number of Euclidean pseudo-order types: nondegenerate abstract order types of configurations of n points in the plane.

Original entry on oeis.org

1, 1, 1, 2, 3, 16, 135, 3315, 158830, 14320182, 2343203071, 691470685682, 366477801792538
Offset: 1

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Author

Keywords

Comments

Also the number of nonisomorphic nondegenerate acyclic rank 3 oriented matroids on n elements. - Manfred Scheucher, May 09 2022

References

  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Formula

Asymptotics: a(n) = 2^(Theta(n^2)). This is Bachmann-Landau notation, that is, there are constants n_0, c, and d, such that for every n >= n_0 the inequality 2^{c n^2} <= a(n) <= 2^{d n^2} is satisfied. For more information see e.g. the Handbook of Discrete and Computational Geometry. - Manfred Scheucher, Sep 12 2019

Extensions

a(11) from Franz Aurenhammer (auren(AT)igi.tu-graz.ac.at), Feb 05 2002
a(12) from Manfred Scheucher and Günter Rote, Aug 31 2019
a(13) from Manfred Scheucher and Günter Rote, Sep 12 2019
Definition clarified by Manfred Scheucher, Jun 22 2023

A060637 Triangle T(n,k) (0 <= k <= n) giving number of tilings of the k-dimensional zonotope constructed from n vectors.

Original entry on oeis.org

1, 2, 1, 4, 2, 1, 8, 6, 2, 1, 16, 24, 8, 2, 1, 32, 120, 62, 10, 2, 1, 64, 720, 908, 148, 12, 2, 1, 128, 5040, 24698, 7686, 338, 14, 2, 1, 256, 40320, 1232944
Offset: 0

Views

Author

N. J. A. Sloane, Apr 16 2001

Keywords

Comments

The zonotope Z(n,k) is the projection of the n-dimensional hypercube onto the k-dimensional space and the tiles are the projections of the k-dimensional faces of the hypercube.
T(n,k) is also the number of signotopes on n elements of rank r=k+1. A signotope on n elements of rank r is a mapping X:{{1..n} choose r}->{+,-} such that for any r+1 indices I={i_0,...,i_r} with i_0 < i_1 < ... < i_r, the sequence X(I-i_0), X(I-i_1), ..., X(I-i_r) changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Feb 09 2022

Examples

			Triangle T(n,k) begins:
    1;
    2,    1;
    4,    2,     1;
    8,    6,     2,    1;
   16,   24,     8,    2,   1;
   32,  120,    62,   10,   2,  1;
   64,  720,   908,  148,  12,  2, 1;
  128, 5040, 24698, 7686, 338, 14, 2, 1;
  ...
		

References

  • A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G. M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46, Second Edition, Cambridge University Press, 1999
  • Victor Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.

Crossrefs

Extensions

Edited by Manfred Scheucher, Mar 08 2022

A060602 Number of tilings of the d-dimensional zonotope constructed from d+3 vectors.

Original entry on oeis.org

8, 24, 62, 148, 338, 752, 1646, 3564, 7658, 16360, 34790, 73700, 155618, 327648, 688094, 1441756, 3014618, 6291416, 13107158, 27262932, 56623058, 117440464, 243269582, 503316428, 1040187338, 2147483592, 4429184966
Offset: 0

Views

Author

Matthieu Latapy (latapy(AT)liafa.jussieu.fr), Apr 12 2001

Keywords

Comments

The zonotope Z(D,d) is the projection of the D-dimensional hypercube onto the d-dimensional space and the tiles are the projections of the d-dimensional faces of the hypercube. Here the codimension, i.e., D-d, is constant = 3 and d >= 0.
Also the number of signotopes on r+2 elements of rank r. A signotope on n elements of rank r is a mapping X:{{1..n} choose r}->{+,-} such that for any r+1 indices I={i_0,...,i_r} with i_0 < i_1 < ... < i_r, the sequence X(I-i_0), X(I-i_1), ..., X(I-i_r) changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Feb 09 2022

Examples

			For any Z(D,d), the number of codimension 0 tilings is always 1, with codimension 1 it is 2, with codimension 2 it is 2.D.
		

References

  • A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G. M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46, Second Edition, Cambridge University Press, 1999.
  • Victor Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.

Crossrefs

Cf. A006245 (two-dimensional tilings), A060595-A060601. A diagonal of A060637. See also A351383 and A351384 for other diagonals.
Cf. A133546.

Programs

  • Mathematica
    LinearRecurrence[{6,-13,12,-4},{8,24,62,148},30] (* Harvey P. Dale, Oct 13 2023 *)
  • Python
    print([2**(n + 1)*(n + 7) - 2*n - 6 for n in range(100)])

Formula

Conjectures from Colin Barker, Feb 20 2013: (Start)
a(n) = 2*(-3+7*2^n+(-1+2^n)*n).
G.f.: -2*(4*x^3-11*x^2+12*x-4) / ((x-1)^2*(2*x-1)^2). (End)
The above conjectures are correct; see Proposition 7.1 in Ziegler's article. - Manfred Scheucher, Feb 09 2022
a(n) = 2 * A133546(n+2). - Alois P. Heinz, Feb 11 2022

Extensions

Edited by Manfred Scheucher, Mar 08 2022

A086903 a(n) = 8*a(n-1) - a(n-2), starting with a(0) = 2 and a(1) = 8.

Original entry on oeis.org

2, 8, 62, 488, 3842, 30248, 238142, 1874888, 14760962, 116212808, 914941502, 7203319208, 56711612162, 446489578088, 3515205012542, 27675150522248, 217885999165442, 1715412842801288, 13505416743244862, 106327921103157608
Offset: 0

Views

Author

Nikolay V. Kosinov (kosinov(AT)unitron.com.ua), Sep 21 2003

Keywords

Comments

a(n+1)/a(n) converges to (4+sqrt(15)) = 7.872983... a(0)/a(1)=2/8; a(1)/a(2)=8/62; a(2)/a(3)=62/488; a(3)/a(4)=488/3842; ... etc. Lim a(n)/a(n+1) as n approaches infinity = 0.127016... = 1/(4+sqrt(15)) = (4-sqrt(15)).
Twice A001091. - John W. Layman, Sep 25 2003
Except for the first term, positive values of x (or y) satisfying x^2 - 8xy + y^2 + 60 = 0. - Colin Barker, Feb 13 2014

Examples

			a(4) = 3842 = 8*a(3) - a(2) = 8*488 - 62 = (4+sqrt(15))^4 + (4-sqrt(15))^4 = 3841.9997397 + 0.0002603 = 3842.
		

Crossrefs

Programs

  • Magma
    I:=[2,8]; [n le 2 select I[n] else 8*Self(n-1)-Self(n-2): n in [1..30]]; // Vincenzo Librandi, Feb 15 2014
  • Mathematica
    a[0] = 2; a[1] = 8; a[n_] := 8a[n - 1] - a[n - 2]; Table[ a[n], {n, 0, 19}] (* Robert G. Wilson v, Jan 30 2004 *)
    CoefficientList[Series[(2 - 8 x)/(1 - 8 x + x^2), {x, 0, 40}], x] (* Vincenzo Librandi, Feb 15 2014 *)
    LinearRecurrence[{8,-1},{2,8},30] (* Harvey P. Dale, Jan 18 2015 *)
  • Sage
    [lucas_number2(n,8,1) for n in range(27)] # Zerinvary Lajos, Jun 25 2008
    

Formula

a(n) = (4+sqrt(15))^n + (4-sqrt(15))^n.
G.f.: (2-8*x)/(1-8*x+x^2). [Philippe Deléham, Nov 02 2008]
From Peter Bala, Jan 06 2013: (Start)
Let F(x) = product {n = 0..inf} (1 + x^(4*n+1))/(1 + x^(4*n+3)). Let alpha = 4 - sqrt(15). This sequence gives the simple continued fraction expansion of 1 + F(alpha) = 2.12474 84992 41370 33639 ... = 2 + 1/(8 + 1/(62 + 1/(488 + ...))). Cf. A174502 and A005248.
Also F(-alpha) = 0.87474 74663 84045 35032 ... has the continued fraction representation 1 - 1/(8 - 1/(62 - 1/(488 - ...))) and the simple continued fraction expansion 1/(1 + 1/((8-2) + 1/(1 + 1/((62-2) + 1/(1 + 1/((488-2) + 1/(1 + ...))))))).
F(alpha)*F(-alpha) has the simple continued fraction expansion 1/(1 + 1/((8^2-4) + 1/(1 + 1/((62^2-4) + 1/(1 + 1/((488^2-4) + 1/(1 + ...))))))).
(End)

A145662 a(n) = numerator of polynomial of genus 1 and level n for m = 5 = A[1,n](5).

Original entry on oeis.org

0, 5, 55, 835, 8365, 41837, 209195, 7321885, 73218955, 1098284605, 5491423277, 302028282755, 1510141416085, 98159192073245, 490795960391965, 2453979801983849, 24539798019883535, 2085882831690821195
Offset: 1

Views

Author

Artur Jasinski, Oct 16 2008

Keywords

Comments

For numerator of polynomial of genus 1 and level n for m = 1 see A001008
Definition: The polynomial A[1,2n+1](m) = A[genus 1,level n] is here defined as
Sum_{d=1..n-1} m^(n-d)/d.
Few first A[1,n](m):
n=1: A[1,1](m)= 0;
n=2: A[1,2](m)= m;
n=3: A[1,3](m)= m/2 + m^2;
n=4: A[1,4](m)= m/4 + m^2/3 + m^3/2 + m^4.
General formula which uses these polynomials is:
(1/(n+1))Hypergeometric2F1[1,n,n+1,1/m] = Sum_{x>=0} m^(-x)/(x+n) = m^n*arctanh((2m-1)/(2m^2-2m+1)) - A[1,n](m) = m^n*log(m/(m-1)) - A[1,n](m).
The sequence of denominators is ?, 1, 2, 6, 12, 12, 12, 84, ... - Matthew J. Samuel, Jan 30 2011

Crossrefs

Programs

  • Maple
    A145662 := proc(n) add( 5^(n-d)/d,d=1..n-1) ; numer(%) ; end proc: # R. J. Mathar, Feb 01 2011
  • Mathematica
    m = 5; aa = {}; Do[k = 0; Do[k = k + m^(r - d)/d, {d, 1, r - 1}]; AppendTo[aa, Numerator[k]], {r, 1, 30}]; aa

A006246 Number of simple arrangements of pseudolines in the projective plane with an oriented marked cell; number of oriented abstract order types of n points (distinguishing mirror-symmetric copies).

Original entry on oeis.org

1, 1, 1, 2, 3, 20, 242, 6405, 316835, 28627261, 4686329954, 1382939012729, 732955581630129
Offset: 1

Views

Author

Keywords

Comments

Previous name was: Number of primitive sorting networks on n elements.

References

  • M. H. Klin et al., "2D-configurations and clique-cyclic orientations of the graphs L(K_p)", pages 149-162 of Reports in Molecular Theory, Vol. 1, 1990.
  • N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).

Crossrefs

Cf. A006245. See A006247 for abstract order types when mirror-symmetric copies are identified.

Extensions

Definition corrected by Günter Rote, Dec 02 2021
a(12) and a(13) from Günter Rote, Mar 04 2025

A060596 Number of tilings of the 4-dimensional zonotope constructed from D vectors.

Original entry on oeis.org

1, 2, 12, 338, 78032, 295118262, 42185916295296
Offset: 4

Views

Author

Matthieu Latapy (latapy(AT)liafa.jussieu.fr), Apr 12 2001

Keywords

Comments

The zonotope Z(D,d) is the projection of the D-dimensional hypercube onto the d-dimensional space and the tiles are the projections of the d-dimensional faces of the hypercube. Here d=4 and D varies.
Also the number of signotopes of rank 5. A signotope of rank r is a mapping X:{{1..n} choose r}->{+,-} such that for any r+1 indices I={i_0,...,i_r} with i_0 < i_1 < ... < i_r, the sequence X(I-i_0), X(I-i_1), ..., X(I-i_r) changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Feb 09 2022

Examples

			For any d, the only possible tile for Z(d,d) is Z(d,d) itself, therefore the first term of the series is 1. It is well known that there are always two d-tilings of Z(d+1,d), therefore the second term is 2. More examples are available on my web page.
		

References

  • A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G.M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46 Second Edition, Cambridge University Press, 1999.
  • Victor Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.

Crossrefs

Cf. A006245 (two-dimensional tilings), A060595-A060602.
Column k=4 of A060637.

Formula

Asymptotics: a(n) = 2^(Theta(n^4)). This is Bachmann-Landau notation, that is, there are constants n_0, c, and d, such that for every n >= n_0 the inequality 2^{c n^4} <= a(n) <= 2^{d n^4} is satisfied. - Manfred Scheucher, Sep 22 2021

Extensions

a(8)-a(9) from Manfred Scheucher, Sep 21 2021
Edited by Manfred Scheucher, Mar 08 2022
a(10) from Manfred Scheucher, Jul 17 2023

A060601 Number of tilings of the 9-dimensional zonotope constructed from D vectors.

Original entry on oeis.org

1, 2, 22, 16360, 613773463394
Offset: 9

Views

Author

Matthieu Latapy (latapy(AT)liafa.jussieu.fr), Apr 12 2001

Keywords

Comments

The zonotope Z(D,d) is the projection of the D-dimensional hypercube onto the d-dimensional space and the tiles are the projections of the d-dimensional faces of the hypercube. Here d=9 and D varies.
Also the number of signotopes of rank 10. A signotope of rank r is a mapping X:{{1..n} choose r}->{+,-} such that for any r+1 indices I={i_0,...,i_r} with i_0 < i_1 < ... < i_r, the sequence X(I-i_0), X(I-i_1), ..., X(I-i_r) changes its sign at most once (see Felsner-Weil reference). - Manfred Scheucher, Feb 09 2022

Examples

			For any d, the only possible tile for Z(d,d) is Z(d,d) itself, therefore the first term of the series is 1. It is well known that there are always two d-tilings of Z(d+1,d), therefore the second term is 2. More examples are available on my web page.
		

References

  • A. Bjorner, M. Las Vergnas, B. Sturmfels, N. White and G.M. Ziegler, Oriented Matroids, Encyclopedia of Mathematics 46 Second Edition, Cambridge University Press, 1999.
  • Victor Reiner, The generalized Baues problem, in New Perspectives in Algebraic Combinatorics (Berkeley, CA, 1996-1997), 293-336, Math. Sci. Res. Inst. Publ., 38, Cambridge Univ. Press, Cambridge, 1999.

Crossrefs

Cf. A006245 (two-dimensional tilings), A060595-A060602.
Column k=9 of A060637.

Formula

Asymptotics: a(n) = 2^(Theta(n^9)). This is Bachmann-Landau notation, that is, there are constants n_0, c, and d, such that for every n >= n_0 the inequality 2^{c n^9} <= a(n) <= 2^{d n^9} is satisfied. - Manfred Scheucher, Sep 22 2021

Extensions

a(13) from Manfred Scheucher, Mar 07 2022
Edited by Manfred Scheucher, Mar 08 2022
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