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

A099085 A bisection of A006966.

Original entry on oeis.org

1, 1, 2, 15, 222, 5994, 262776, 16873364, 1471613387, 165269824761
Offset: 0

Views

Author

N. J. A. Sloane, Nov 15 2004

Keywords

A099086 A bisection of A006966.

Original entry on oeis.org

1, 1, 5, 53, 1078, 37622, 2018305, 152233518, 15150569446
Offset: 0

Views

Author

N. J. A. Sloane, Nov 15 2004

Keywords

A006982 Number of unlabeled distributive lattices on n nodes.

Original entry on oeis.org

1, 1, 1, 1, 2, 3, 5, 8, 15, 26, 47, 82, 151, 269, 494, 891, 1639, 2978, 5483, 10006, 18428, 33749, 62162, 114083, 210189, 386292, 711811, 1309475, 2413144, 4442221, 8186962, 15077454, 27789108, 51193086, 94357143, 173859936, 320462062, 590555664, 1088548290, 2006193418, 3697997558, 6815841849, 12563729268, 23157428823, 42686759863, 78682454720, 145038561665, 267348052028, 492815778109, 908414736485
Offset: 0

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Author

Keywords

References

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

Crossrefs

Extensions

More terms from Jobst Heitzig (heitzig(AT)math.uni-hannover.de), Feb 02 2001. These were computed by the same algorithm that was used to enumerate the posets on 14 elements.

A354493 Number of quantales on n elements, up to isomorphism.

Original entry on oeis.org

1, 2, 12, 129, 1852, 33391, 729629, 19174600, 658343783
Offset: 1

Views

Author

Arman Shamsgovara, May 28 2022

Keywords

Comments

A quantale is an algebraic structure (X,*,v) composed of a set X of elements, a semigroup operator "*" and a supremum operator "v" (in the sense of lattices) such that * distributes over v: x * (y v z) = (x * y) v (x * z) and (x v y) * z = (x * z) v (y * z) for all elements x,y,z in X. In addition the bottom element corresponding to v, denoted 0, must satisfy x * 0 = 0 * x = 0.

References

  • P. Eklund, J. G. García, U. Höhle, and J. Kortelainen, (2018). Semigroups in complete lattices. In Developments in Mathematics (Vol. 54). Springer Cham.
  • K. I. Rosenthal, Quantales and their applications. Longman Scientific and Technical, 1990.
  • Arman Shamsgovara, A catalogue of every quantale of order up to 9 (abstract, to appear), LINZ2022, 39th Linz Seminar on Fuzzy Set Theory, Linz, Austria.
  • Arman Shamsgovara and P. Eklund, A Catalogue of Finite Quantales, GLIOC Notes, December 2019.

Crossrefs

Related algebraic structures: A027851, A006966.

Programs

  • Mace4
    assign(max_models,-1).
    assign(domain_size,4).
    formulas(assumptions).
    % Comment: This will find all quantales on 4 elements, fixing
    % 0 as the bottom and 3 as the top. Elements will be numbered
    % 0-3. Results *must* be run through the companion program
    % isofilter that is included with the downloads for mace4,
    % otherwise the output will contain isomorphic duplicates!
    % By changing the domain size, this file should be sufficient
    % for up to 6 elements, but will crash for higher numbers.
    (x*y)*z = x*(y*z).
    (x v y) v z = x v (y v z).
    x v y = y v x.
    x v x = x.
    x*(y v z) = (x*y) v (x*z).
    (x v y)*z = (x*z) v (y*z).
    0*x = 0.
    x*0 = 0.
    0 v x = x.
    3 v x = 3.
    end_of_list.
    formulas(goals).
    end_of_list.

A006981 a(n) is the number of unlabeled modular lattices on n nodes.

Original entry on oeis.org

1, 1, 1, 1, 2, 4, 8, 16, 34, 72, 157, 343, 766, 1718, 3899, 8898, 20475, 47321, 110024, 256791, 601991, 1415768, 3340847, 7904700, 18752943, 44588803, 106247120, 253644319, 606603025, 1453029516, 3485707007, 8373273835, 20139498217, 48496079939, 116905715114, 282098869730
Offset: 0

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Author

Keywords

Examples

			From _Jukka Kohonen_, Mar 06 2021: (Start)
a(5)=4: These are the four lattices.
  o     o       o        o
  |     |      / \      /|\
  o     o     o   o    o o o
  |    / \     \ /      \|/
  o   o   o     o        o
  |    \ /      |
  o     o       o
  |
  o
(End)
		

References

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

Crossrefs

Cf. A006966 (lattices), A006982 (distributive), A342132 (modular vertically indecomposable).

Extensions

More terms from Nathan Lawless, Sep 15 2013
Corrected a(24) and added a(25)-a(30) by Jukka Kohonen, Aug 15 2017
a(31)-a(32) from Jukka Kohonen, Sep 23 2018
Name clarified by Jukka Kohonen, Sep 23 2018
a(33) from Jukka Kohonen, Sep 26 2018
a(34)-a(35) from Jukka Kohonen, Mar 06 2021

A055512 Lattices with n labeled elements.

Original entry on oeis.org

1, 1, 2, 6, 36, 380, 6390, 157962, 5396888, 243179064, 13938711210, 987858368750, 84613071940452, 8597251494954564, 1020353444641839854, 139627532137612581090, 21788453795572514675760, 3840596246648027262079472, 758435490711709577216754642
Offset: 0

Views

Author

Jobst Heitzig (heitzig(AT)math.uni-hannover.de), Jul 03 2000

Keywords

Crossrefs

Cf. A006966, A001035. Main diagonal of A058159.

A058116 Triangle read by rows: T(n,k) is the number of isomorphism classes of commutative semigroups of order n with k idempotents.

Original entry on oeis.org

1, 2, 1, 5, 5, 2, 16, 23, 14, 5, 62, 106, 93, 49, 15, 342, 544, 582, 422, 200, 53, 3435, 3380, 3773, 3360, 2178, 943, 222, 97061, 30788, 27222, 26625, 21283, 12676, 5072, 1078
Offset: 1

Views

Author

Christian G. Bower, Nov 09 2000

Keywords

Examples

			Triangle begins:
   1;
   2,   1;
   5,   5,  2;
  16,  23, 14,  5;
  62, 106, 93, 49, 15;
  ...
		

Crossrefs

Row sums give A001426.
Main diagonal is A006966(n+1).
Column 1 is A058117.
The labeled version is A058167.

Extensions

a(29)-a(36) from Andrew Howroyd, Jan 27 2022

A058142 Triangle read by rows: number of commutative monoids of order n with k idempotents.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 2, 9, 6, 2, 1, 26, 30, 16, 5, 1, 98, 142, 111, 54, 15, 1, 455, 718, 713, 482, 215, 53, 3, 4018, 4277, 4637, 3919, 2414, 996, 222, 2, 101910, 36124, 32937, 31308, 24047, 13758, 5294, 1078, 1, 10054303, 708355, 290278, 260758, 229411, 164216, 88178, 31867, 5994
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000

Keywords

Examples

			Triangle begins:
  1;
  1,  1;
  1,  3,   1;
  2,  9,   6,   2;
  1, 26,  30,  16, 5;
  1, 98, 142, 111, 54, 15;
  ...
		

Crossrefs

Row sums give A058131.
Main diagonal: A006966.
Columns 1..2: A000688, A058143.

Extensions

a(30)-a(55) from Andrew Howroyd, Feb 15 2022

A343161 Number of planar distributive lattices with n nodes.

Original entry on oeis.org

1, 1, 1, 2, 3, 5, 8, 14, 24, 42, 72, 127, 221, 390, 684, 1207, 2125, 3753, 6620, 11698, 20659, 36518, 64533, 114099, 201707, 356683, 630693, 1115370, 1972469, 3488489, 6169656, 10912003, 19299555, 34135099, 60374747, 106786342, 188875933, 334072759, 590889162, 1045136443
Offset: 1

Views

Author

N. J. A. Sloane, Apr 18 2021, following a suggestion from Allan C. Wechsler

Keywords

Crossrefs

Programs

  • PARI
    V=concat(digits(1101010214296),[21,18,48,50,114,135,277,358,681]); P=List(1); for(n=2,#V,listput(P,V[2..n]*Colrev(P))); A343161=Vec(P) \\ M. F. Hasler, Jun 22 2021, using V[1..22] & formula from Bianca Newell
    
  • PARI
    \\ Needs S, V defined in A345734.
    seq(n)={Vec(x/(1 - x - Ser((S(n)+V(n))/2)))} \\ Andrew Howroyd, Jan 24 2023
  • Python
    v=[1,1,1,0,1,0,1,0,2,1,4,2,9,6,21,18,48,50,114,135,277,358,681]
    p=[1,1,1]
    for n in range(3,23):
        p=p+[sum(v[k]*p[n-k+1] for k in range(2,n+1))]
    p # Bianca Newell, Jun 22 2021
    

Formula

a(n) = Sum_{k=2..n} V(k)*a(n-k+1), where V(k) is the number of planar vertically indecomposable distributive lattices of size k. - Bianca Newell, Jun 22 2021
G.f.: x/(2 - B(x)/x) where B(x) is the g.f of A345734. - Andrew Howroyd, Jan 24 2023

Extensions

a(16)-a(22), computed with Python code, from Bianca Newell, Jun 22 2021
Terms a(23) and beyond from Andrew Howroyd, Jan 24 2023

A058800 Vertically indecomposable lattices on n unlabeled nodes.

Original entry on oeis.org

1, 1, 1, 0, 1, 2, 7, 27, 126, 664, 3954, 26190, 190754, 1514332, 12998035, 119803771, 1178740932, 12316480222, 136060611189, 1582930919092, 19328253734491
Offset: 0

Views

Author

Christian G. Bower, Dec 28 2000

Keywords

References

  • J. Heitzig and J. Reinhold, Counting finite lattices, Algebra Universalis, 48 (2002), 43-53.

Crossrefs

a(n+1) is Inverse INVERT transform of A006966(n+1).

Programs

  • Mathematica
    A006966 = Cases[Import["https://oeis.org/A006966/b006966.txt", "Table"], {, }][[All, 2]];
    nmax = Length[A006966] - 1;
    B[x_] = Sum[A006966[[n + 1]] x^n, {n, 0, nmax}];
    A[x_] = Sum[c[n] x^n, {n, 0, nmax}];
    sol = CoefficientList[1 + A[x] - 1/(1 - B[x]) + O[x]^nmax, x] == 0 // Solve // First // Rest // Quiet;
    a[n_] := If[n <= 2, 1, c[n - 2] /. sol];
    a /@ Range[0, nmax] (* Jean-François Alcover, Dec 05 2019 *)

Extensions

a(19) (computed by Jipsen and Lawless) and a(20) from Volker Gebhardt, Sep 28 2016
Showing 1-10 of 22 results. Next