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 16 results. Next

A118601 Partial sums of A058129.

Original entry on oeis.org

1, 3, 10, 45, 273, 2510, 34069, 1703066
Offset: 1

Views

Author

Jonathan Vos Post, May 08 2006

Keywords

Crossrefs

Formula

a(n) = SUM[i=1..n] A058129(i). a(n) = SUM[i=1..n] (2*A058133(i) - A058132(i)).

Extensions

One more term from Jonathan Vos Post, Jul 20 2009
Edited by N. J. A. Sloane, Jul 25 2009

A058133 Number of monoids (semigroups with identity) of order n, considered to be equivalent when they are isomorphic or anti-isomorphic (by reversal of the operator).

Original entry on oeis.org

0, 1, 2, 6, 27, 156, 1373, 17730, 858977, 1844075697, 52991253973742
Offset: 0

Views

Author

Christian G. Bower, Nov 13 2000

Keywords

Crossrefs

Formula

a(n)=(A058129(n)+A058132(n))/2.

Extensions

a(8) and a(9) from Distler & Kelsey (2008), added by N. J. A. Sloane, Jul 10 2009
a(10) from Distler & Kelsey (2009), added by Max Alekseyev, Jul 13 2009
a(0) prepended by Jianing Song, Oct 26 2019

A058137 Triangle read by rows: monoids of order n with k idempotents.

Original entry on oeis.org

1, 1, 1, 1, 3, 3, 2, 9, 14, 10, 1, 32, 63, 86, 46, 2, 219, 406, 694, 665, 251, 1, 5585, 3331, 6343, 8582, 6035, 1682, 5
Offset: 1

Views

Author

Christian G. Bower, Nov 14 2000

Keywords

Examples

			1; 1,1; 1,3,3; 2,9,14,10; 1,32,63,86,46; ...
		

Crossrefs

Row sums give A058129. Main diagonal: A058112(n-1). Columns 1-3: A000001, A058138, A058139.

A125696 Number of categories with n morphisms.

Original entry on oeis.org

1, 1, 3, 11, 55, 329, 2858, 36440, 1723286, 3687822810
Offset: 0

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Author

Keywords

Examples

			The 11 categories with 3 morphisms consist of:
* 7=A058129(3) categories with 1 object (monoids),
* 3 categories with 2 objects, consisting of: 2=A058129(2) disconnected combinations of a 2-element monoid and a 1-element monoid, and the category with 2 objects and a single morphism between the two objects,
* 1 category with 3 objects (3 separate 1-element monoids).
		

Crossrefs

Formula

Euler transform of A125698.
G.f.: Product_{i>=1} 1/(1-x^i)^A125698(i).
From Elijah Beregovsky, May 13 2025 (Start)
a(n) >= A058129(n).
Conjecture: a(n) = A058129(n)*(1+o(n)). See Cruttwell presentation in Links. (End)

Extensions

a(0) and a(7)-a(9) from Thomas Anton, from the work of G. Cruttwell and R. Leblanc, Jan 25 2019

A125697 Table, T(n,k) is the number of categories with n morphisms and k objects.

Original entry on oeis.org

1, 2, 1, 7, 3, 1, 35, 16, 3, 1, 228, 77, 20, 3, 1, 2237, 485, 111, 21, 3, 1, 31559, 4013, 716, 127, 21, 3, 1, 1668997, 47648, 5623, 862, 131, 21, 3, 1, 3685886630, 1868157, 60201, 6739, 926, 132, 21, 3, 1
Offset: 1

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Author

Keywords

Comments

This is a two-dimensional Euler transform of A125699.

Examples

			The table starts:
     1;
     2,   1;
     7,   3,   1;
    35,  16,   3,  1;
   228,  77,  20,  3, 1;
  2237, 485, 111, 21, 3, 1;
  ...
		

Crossrefs

Cf. A125696 (row sums), A058129 (column 1), A125699, A125701.

Formula

G.f.: Product_{i>=1} Product_{j=1..ceiling(i/2)} 1/(1 - x^i y^j)^A125699(i,j).
T(n,k) = A125701(n-k) when k >= (2/3)*n.
From Ben Spitz, Aug 30 2023: (Start)
T(3n,2n) = T(3n-1,2n-1) + 1 when n >= 1.
T(3n-1,2n-1) = T(3n-2,2n-2) + 4 when n >= 2.
T(3n-2,2n-2) = T(3n-3,2n-3) + 19 when n >= 4.
(End)

Extensions

a(23)-a(29) from Ben Spitz, Jul 17 2023
a(30)-a(36) from Ben Spitz, Aug 29 2023
a(37)-a(45) from Elijah Beregovsky, after the work of Cruttwell and Leblanc, May 20 2025

A058132 Number of self-converse monoids (semigroups with identity) of order n.

Original entry on oeis.org

0, 1, 2, 5, 19, 84, 509, 3901, 48957
Offset: 0

Views

Author

Christian G. Bower, Nov 13 2000

Keywords

Crossrefs

Formula

a(n) = A058133(n)*2 - A058129(n).

Extensions

a(8) from Max Alekseyev, Jul 13 2009
a(0) prepended by Jianing Song, Oct 26 2019

A125699 Table, T(n,k) is the number of connected categories with n morphisms and k objects.

Original entry on oeis.org

1, 2, 7, 1, 35, 6, 228, 28, 2, 2237, 159, 11, 31559, 1075, 77, 3, 1668997, 9389, 497, 24
Offset: 1

Views

Author

Keywords

Comments

Connected in the sense that if the morphism direction and composition is ignored, resulting in a multigraph, that multigraph is connected.

Examples

			The table starts:
        1;
        2;
        7,    1;
       35,    6;
      228,   28,   2;
     2237,  159,  11;
    31559, 1075,  77,  3;
  1668997, 9389, 497, 24;
  ...
		

Crossrefs

Cf. A125696, A125698 (row sums), A110654 (row lengths), A058129 (column 1), A125700 (diagonal sums), A125702 (T(2n-1, n)).

Extensions

a(14)-a(20) from Ben Spitz, Sep 02 2023

A253950 Number of finite, negative, totally ordered monoids of size n (semigroups with a neutral element that is also the top element).

Original entry on oeis.org

1, 1, 2, 8, 44, 308, 2641, 27120, 332507, 5035455
Offset: 1

Views

Author

Milan Petrík, Jan 20 2015

Keywords

Comments

The terms have been computed using the algorithm described in the referenced papers.

Crossrefs

Extensions

a(10) from Milan Petrík, May 09 2021

A058131 Number of isomorphism classes of commutative monoids (commutative semigroups with identity) of order n.

Original entry on oeis.org

0, 1, 2, 5, 19, 78, 421, 2637, 20486, 246458, 11833361
Offset: 0

Views

Author

Christian G. Bower, Nov 13 2000

Keywords

Crossrefs

Row sums of A058142.
Cf. A001426, A058129, A058155 (labeled).

Extensions

a(0) prepended by Jianing Song, Oct 26 2019
a(8) and a(9) from Alex Meiburg, Oct 20 2021
a(10) from Andrew Howroyd, Feb 15 2022

A253948 Number of finite, negative, Archimedean, commutative, totally ordered monoids of size n (semi-groups with a neutral element that is also the top element).

Original entry on oeis.org

1, 1, 1, 2, 6, 22, 95, 471, 2670, 17387, 131753, 1184059, 12896589
Offset: 1

Views

Author

Milan Petrík, Jan 20 2015

Keywords

Comments

Also number of Archimedean triangular norms on an n-chain.
The terms have been computed using the algorithm described in the referenced papers.

Crossrefs

Extensions

a(13) from Milan Petrík, May 09 2021
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