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.

A143109 Let H(2,d) be the space of polynomials p(x,y) of two variables with nonnegative coefficients such that p(x,y)=1 whenever x + y = 1. a(n) is the number of different polynomials in H(2,d) with exactly n distinct monomials and of maximum degree minus two, i.e., of degree 2n-5.

Original entry on oeis.org

0, 0, 0, 11, 38, 88, 198
Offset: 1

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Author

Jiri Lebl (jlebl(AT)math.uiuc.edu), Jul 25 2008

Keywords

Comments

It is unknown but conjectured that this is a sequence of finite numbers. Note that if we went one degree lower and look at polynomials of degree 2n-6, then there are infinitely many if any exist in H(2,d).
Likely an erroneous version of A387029. - Sean A. Irvine, Aug 13 2025

Crossrefs

Programs

  • Mathematica
    (* See the paper by Lebl-Lichtblau. *)

A386841 Triangle read by rows: T(n,k) is the number of fundamental one-dimensional discrete statistical models with rational maximum likelihood estimator supported on the n-dimensional probability simplex and of degree 2n-k (n>=1, 1<=k<=n).

Original entry on oeis.org

1, 1, 3, 2, 4, 12, 4, 10, 38, 82, 2, 24, 88, 254, 602, 4, 32, 198, 643, 2421, 6710, 8, 56, 332, 1442, 6445, 23285, 83906, 4
Offset: 1

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Author

Carlos Améndola, Aug 12 2025

Keywords

Comments

The range of k is precisely chosen so that T(n,k) is positive. That is, whenever the degree is higher than 2n-1 or lower than n, there are no fundamental models.

Examples

			When n=1 then k=1 and the unique model T(1,1)=1 corresponds to the model described by a Bernoulli random variable that assigns probabilities 1-t and t to two possible states, 0<=t<=1. This line segment parametrizes the 1-dimensional probability simplex.
When n=2 we have 1<=k<=2. The T(2,1)=1 unique fundamental model with degree 3 corresponds to the parametrization t -> ((1-t)^3, 3t(1-t), t^3) and the T(2,2)=3 fundamental models of degree 2 correspond to the parametrizations ((1-t)^2, 2t(1-t), t^2) , (1-t, t(1-t), t^2) and ((1-t)^2, t(1-t), t).
Continuing in this way, the first five rows (1<=n<=5) of the fundamental models triangle are:
  1
  1 3
  2 4 12
  4 10 38 82
  2 24 88 254 602
		

Crossrefs

Columns 1..4 are A143107, A143108, A387029, A386840.

A386840 Number of fundamental one-dimensional discrete statistical models with rational maximum likelihood estimator supported on n states and of degree 2n-6.

Original entry on oeis.org

0, 0, 0, 0, 82, 254, 643, 1442
Offset: 1

Views

Author

Carlos Améndola, Aug 05 2025

Keywords

Comments

Unlike A143107 and A143108 (and conjecturally A143109), there are infinitely many polynomials in H(2,d) of degree 2n-6. Nevertheless, this sequence consists of finite numbers.

Crossrefs

Showing 1-3 of 3 results.