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 1-7 of 7 results.

A152789 Football tournament numbers with distinct point totals: number of point series in A064626 in which no two teams have the same total number of points.

Original entry on oeis.org

1, 1, 3, 13, 84, 578, 3931, 26258, 173708, 1143860, 7516179, 49344260
Offset: 1

Views

Author

Jon E. Schoenfield, Dec 13 2008

Keywords

Comments

Only 2 outcomes exist in which all scores are distinct and prime: a 6-team series, [2,3,5,7,11,13] and an 8-team series, [2,3,5,7,11,13,17,19].

Examples

			For 2 teams, [0,3] is the only possible outcome with no repeated point totals, so a(2) = 1.
For 3 teams, the only outcomes are [0,3,6], [1,2,4] and [1,3,4], so a(3) = 3.
		

Crossrefs

Cf. A064626.

A007747 Number of nonnegative integer points (p_1,p_2,...,p_n) in polytope defined by p_0 = p_{n+1} = 0, 2p_i - (p_{i+1} + p_{i-1}) <= 2, p_i >= 0, i=1,...,n. Number of score sequences in a chess tournament with n+1 players (with 3 outcomes for each game).

Original entry on oeis.org

1, 2, 5, 16, 59, 247, 1111, 5302, 26376, 135670, 716542, 3868142, 21265884, 118741369, 671906876, 3846342253, 22243294360, 129793088770, 763444949789, 4522896682789, 26968749517543, 161750625450884
Offset: 0

Views

Author

P. Di Francesco (philippe(AT)amoco.saclay.cea.fr), N. J. A. Sloane

Keywords

Comments

A correspondence between the points in the polytope and the chess scores was found by Svante Linusson (linusson(AT)matematik.su.se):
The score sequences are partitions (a_1,...,a_n) of 2C(n,2) of length <= n that are majorized by 2n,2n-2,2n-4,...,2,0; i.e. f(n,k) := 2n+2n-2+...+(2n-2k+2)-(a_1+a_2+...+a_k) >= 0 for all k. The sequence 0=f(n,0),f(n,1),f(n,2),...,f(n,n)=0 is in the polytope. This establishes the bijection.

Examples

			With 3 players the possible scores sequences are {{0,2,4}, {0,3,3}, {1,1,4}, {1,2,3}, {2,2,2}}.
With 4 players they are {{0,2,4,6}, {0,2,5,5}, {0,3,3,6}, {0,3,4,5}, {0,4,4,4}, {1,1,4,6}, {1,1,5,5}, {1,2,3,6}, {1,2,4,5}, {1,3,3,5}, {1,3,4,4}, {2,2,2,6}, {2,2,3,5}, {2,2,4,4}, {2,3,3,4}, {3,3,3,3}}.
		

References

  • P. A. MacMahon, Chess tournaments and the like treated by the calculus of symmetric functions, Coll. Papers I, MIT Press, 344-375.

Crossrefs

Programs

  • Mathematica
    f[K_, L_, S_, X_] /; K > 1 && L <= S/K <= X + 1 - K := f[K, L, S, X] = Sum[f[K - 1, i, S - i, X], {i, L, Floor[S/K]}]; f[1, L_, S_, X_] /; L <= S <= X = 1; f[, , , ] = 0; a[n_] := f[n + 1, 0, n*(n + 1), 2*n]; Table[a[n], {n, 0, 21}] (* Jean-François Alcover, Jul 13 2012, after Jon E. Schoenfield *)

Formula

Schoenfield (see Comments link) gives a recursive method for computing this sequence.

Extensions

More terms from David W. Wilson

A047730 Number of score sequences in tournament with n players, when 4 points are awarded in each game.

Original entry on oeis.org

1, 3, 13, 76, 521, 3996, 32923, 286202, 2590347, 24203935, 232050202, 2272449745, 22653570386, 229274897514, 2350933487206, 24381053759852, 255382755251622, 2698732882975782, 28743579211912338
Offset: 1

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Author

Keywords

References

  • P. A. MacMahon, Chess tournaments and the like treated by the calculus o symmetric functions, Coll. Papers I, MIT Press, 344-375.

Crossrefs

Formula

Nonnegative integer points (p_1, p_2, ..., p_n) in polytope p_0=p_{n+1}=0, 2p_i -(p_{i+1}+p_{i-1}) <= 4, p_i >= 0, i=1, ..., n.

A064422 Football league numbers: the possible point series for a league of n teams playing each other twice where for each match 3 points are awarded to the winning team and 1 to each in the case of a tie.

Original entry on oeis.org

1, 4, 40, 748, 13744, 238568, 4054190
Offset: 1

Views

Author

Thomas Schulze (jazariel(AT)tiscalenet.it), Sep 30 2001

Keywords

Comments

This sequence reflects the now common 3-point rule of international football where the sum of total points awarded depends on the outcome of each match. The classical 2-point rule is equivalent of that for chess tournaments (A047730).

Examples

			For 2 teams there are 4 possible outcomes: [0, 6], [1, 4], [2, 2] and [3, 3], so a(2) = 4.
		

Crossrefs

Extensions

a(6)-a(7) from Lorand Lucz, Mar 09 2012

A317723 Round-robin tournament numbers: The number of possible point series for a tournament of n teams playing each other once where n points are awarded to the winning team and 1 to each in the case of a tie. A team winning more games than another always has a higher point score.

Original entry on oeis.org

1, 2, 7, 40, 367, 4828, 82788, 1750152
Offset: 1

Views

Author

Donghwi Park, Aug 05 2018

Keywords

Comments

The 3-point rule is equivalent to that for football (A064626).
The classical 2-point rule is equivalent to that for chess tournaments (A007747).

Examples

			a(1)..a(4) are the same as in A064626.
		

Crossrefs

Programs

  • Python
    def play(ps, n, r, i, j):
        if j>=n:
            ps.add(tuple(sorted(r)))
        else:
            (ni,nj) = (i,j+1) if j<(n-1) else (i+1,i+2)
            s=list(r)
            s[i]=r[i]+n; play(ps,n,s,ni,nj)
            s[i]=r[i]+1; s[j]=r[j]+1; play(ps,n,s,ni,nj)
            s[i]=r[i]  ; s[j]=r[j]+n; play(ps,n,s,ni,nj)
    def A317723(n):
        ps=set()
        play(ps,n,[0]*n,0,1)
        return len(ps)
    # Bert Dobbelaere, Oct 07 2018

Extensions

a(6)-a(8) from Bert Dobbelaere, Oct 07 2018

A209467 Football league numbers with distinct point totals for a league of n teams playing each other twice where for each match 3 points are awarded to the winning team and 1 to each in the case of a tie.

Original entry on oeis.org

1, 2, 25, 408, 6272, 91640, 1316363
Offset: 1

Views

Author

Lorand Lucz, Mar 09 2012

Keywords

Examples

			For n=2 the possible outcomes are [0,6] and [1,4], so a(2)=2.  The other possible outcomes [2,2] and [3,3] do not have distinct point totals.
		

Crossrefs

A064422 allows teams to have the same point total.

A330637 Number of n-team football tournament outcomes that can be obtained in a single way. Each team plays each other team once, where 3 points are awarded to the winning team and 1 to each team in the case of a draw.

Original entry on oeis.org

1, 2, 6, 25, 106, 436, 1795, 7487
Offset: 1

Views

Author

Dmitry Kamenetsky, Dec 22 2019

Keywords

Comments

Since such outcomes are obtained in a single way, their individual games can be uniquely reconstructed. This allows them to be used in a reconstruction puzzle (see links).

Examples

			For 2 teams there are 2 outcomes that can be obtained in a single way: [0, 3] and [1, 1], so a(2) = 2.
For 3 teams there are 6 outcomes that can be obtained in a single way: [0, 3, 6], [1, 3, 4], [1, 1, 6], [1, 2, 4], [0, 4, 4] and [2, 2, 2], so a(3) is 6. Note that the outcome [3, 3, 3] can be obtained in two ways: (A beats B, B beats C, C beats A) or (B beats A, A beats C, C beats B).
		

Crossrefs

Cf. A064626 counts all outcomes.

Extensions

a(7) from Giovanni Resta, Jan 02 2020
a(8) from Andrew Howroyd, Feb 28 2020
Showing 1-7 of 7 results.