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 1-3 of 3 results.

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

A253949 Number of finite, negative, Archimedean, 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, 8, 44, 333, 3543, 54954, 1297705, 47542371
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(11) from Milan Petrík, May 09 2021

A374293 a(n)/binomial(n,2)! is the probability that the minimum spanning tree of the complete graph of n vertices with i.i.d. random edge weights is a specific path.

Original entry on oeis.org

1, 1, 2, 44, 27120, 882241920, 2443792425984000, 846533597741050576896000, 50571850611494440562578575851520000, 686805008584962439650318114385825747697664000000, 2701735270674169239689693528384644314472371275610193920000000000, 3819958423456547324072333722421751679308286064300212197312630212725309440000000000
Offset: 1

Views

Author

Jamie Tucker-Foltz, Jul 02 2024

Keywords

Comments

Equivalently, a(n) is the number of orderings of the edges of the complete graph of n vertices such that the minimal spanning tree (e.g., obtained by running Kruskal's algorithm with the edges in that order) is a specific path.
It appears that this is a subsequence of A253950. Specifically, a(n) appears at index m - n + 3, where m = binomial(n,2) is the number of edges of the complete graph on n vertices.

Examples

			a(3) = 2 because there are 2 orderings of the edges a, b, and c of K_3 that give the path {a, b}: (a, b, c) and (b, a, c).
		

Crossrefs

Programs

  • PARI
    E(p,m)={sum(k=0, m, sum(i=0, k, polcoef(p, i)*i!*(m-i)! )*x^k/(k!*(m-k)!))}
    seq(n)={my(v=vector(n)); v[1]=1; for(n=2, n, my(p=sum(k=1, n-1, v[k]*v[n-k])); v[n]=E(intformal(p), binomial(n,2))); vector(n, n, my(m=binomial(n,2)); m!*polcoef(v[n], m))} \\ Andrew Howroyd, Jul 31 2024
Showing 1-3 of 3 results.