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 21 results. Next

A068029 Table of sorted score sequences (including duplications), with A000571 giving the number of score sequences of length n.

Original entry on oeis.org

0, 0, 1, 0, 1, 2, 1, 1, 1, 0, 1, 2, 3, 0, 2, 2, 2, 1, 1, 1, 3, 1, 1, 2, 2, 0, 1, 2, 3, 4, 0, 1, 3, 3, 3, 0, 2, 2, 2, 4, 0, 2, 2, 3, 3, 1, 1, 1, 3, 4, 1, 1, 2, 2, 4, 1, 1, 2, 3, 3, 1, 2, 2, 2, 3, 2, 2, 2, 2, 2, 0, 1, 2, 3, 4, 5, 0, 1, 2, 4, 4, 4, 0, 1, 3, 3, 3, 5, 0, 1, 3, 3, 4, 4, 0, 2, 2, 2, 4, 5, 0, 2
Offset: 1

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Author

Eric W. Weisstein, Feb 10 2002

Keywords

Examples

			{0} is the score sequence of length 1.
{0,1} is the score sequence of length 2.
{0,1,2} and {1,1,1} are the two score sequences of length 3.
		

Crossrefs

Cf. A000571.

A046917 Erroneous version of A000571.

Original entry on oeis.org

1, 1, 2, 4, 9, 22, 59, 169, 506, 1586
Offset: 1

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Author

Keywords

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

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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.

A047729 Number of score sequences in tournament with n players, when 3 points are awarded in each game.

Original entry on oeis.org

1, 2, 8, 37, 198, 1178, 7548, 50944, 357855, 2595250, 19313372, 146815503, 1136158495, 8927025989, 71065654235, 572215412354, 4653746621835, 38184724333615, 315792633485360, 2630183440412617, 22046522161472304
Offset: 1

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Author

Keywords

References

  • P. A. MacMahon, Chess tournaments and the like treated by the calculus of 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}) <= 3, p_i >= 0, i=1, ..., n.

A047731 Number of score sequences in tournament with n players, when 5 points are awarded in each game.

Original entry on oeis.org

1, 3, 18, 131, 1111, 10461, 105819, 1127413, 12499673, 143021541, 1678718575, 20123155604, 245521479531, 3041006378312, 38157059717410, 484209044329613, 6205758830280388, 80235572611152385
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

A145855 Number of n-element subsets of {1,2,...,2n-1} whose elements sum to a multiple of n.

Original entry on oeis.org

1, 1, 4, 9, 26, 76, 246, 809, 2704, 9226, 32066, 112716, 400024, 1432614, 5170604, 18784169, 68635478, 252085792, 930138522, 3446167834, 12815663844, 47820414962, 178987624514, 671825133644, 2528212128776, 9536894664376
Offset: 1

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Author

T. D. Noe, Oct 21 2008, Oct 22 2008, Oct 24 2008

Keywords

Comments

It is easy to see that {1,2,...,2n-1} can be replaced by any 2n-1 consecutive numbers and the results will be the same. Erdos, Ginzburg and Ziv proved that every set of 2n-1 numbers -- not necessarily consecutive -- contains a subset of n elements whose sum is a multiple of n.

Examples

			a(3)=4 because, of the 10 3-element subsets of 1..7, only {1,2,3}, {1,3,5}, {2,3,4} and {3,4,5} have sums that are multiples of 3.
L.g.f.: L(x) = x + x^2/2 + 4*x^3/3 + 9*x^4/4 + 26*x^5/5 + 76*x^6/6 + 246*x^7/7 +...
where exponentiation yields the g.f. of A000571:
exp(L(x)) = 1 + x + x^2 + 2*x^3 + 4*x^4 + 9*x^5 + 22*x^6 + 59*x^7 + 167*x^8 +...
		

Crossrefs

Column k=2 of A309148.

Programs

  • Mathematica
    Table[Length[Select[Plus@@@Subsets[Range[2n-1],{n}], Mod[ #,n]==0&]], {n,10}]
    Table[d=Divisors[n]; Sum[(-1)^(n+d[[i]]) EulerPhi[n/d[[i]]] Binomial[2d[[i]], d[[i]]]/2/n, {i,Length[d]}], {n,30}] (* T. D. Noe, Oct 24 2008 *)
  • PARI
    {a(n)=sumdiv(n, d, (-1)^(n+d)*eulerphi(n/d)*binomial(2*d, d)/(2*n))}
    
  • PARI
    {A227532(n, k)=local(G=1); for(i=1, n, G=1+x*subst(G, x, q*x)*G +x*O(x^n)); n*polcoeff(polcoeff(log(G), n, x), k, q)}
    {a(n)=sum(k=0,n\2, A227532(n, n*k))} \\ Paul D. Hanna, Jul 17 2013

Formula

a(n) = (1/(2*n))*Sum_{d|n} (-1)^(n+d)*phi(n/d)*binomial(2*d,d). Conjectured by Vladeta Jovovic, Oct 22 2008; proved by Max Alekseyev, Oct 23 2008 (see link).
a(2n+1) = A003239(2n+1) and a(2n) = A003239(2n) - A003239(d), where d is the largest odd divisor of n. - T. D. Noe, Oct 24 2008
a(n) = Sum_{d|n} (-1)^(n+d)*d*A131868(d). - Vladeta Jovovic, Oct 28 2008
a(n) = Sum_{k=0..[n/2]} A227532(n,n*k), where A227532 is the logarithmic derivative, wrt x, of the g.f. G(x,q) = 1 + x*G(q*x,q)*G(x,q) of triangle A227543. - Paul D. Hanna, Jul 17 2013
Logarithmic derivative of A000571, the number of different scores that are possible in an n-team round-robin tournament. - Paul D. Hanna, Jul 17 2013
G.f.: -Sum_{m >= 1} (phi(m)/m) * log((1 + sqrt(1 + 4*(-y)^m))/2). - Petros Hadjicostas, Jul 15 2019
a(n) ~ 2^(2*n-1) / (sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Mar 28 2023

Extensions

Extension T. D. Noe, Oct 24 2008

A046919 Maximal coefficient of polynomial p(n), with p(3)=1, p(n) = (1 - t^(2*n - 4))*(1 - t^(2*n - 3))*p(n - 1)/((1 - t^(n - 3))*(1 - t^n)).

Original entry on oeis.org

1, 1, 3, 8, 24, 73, 227, 734, 2430, 8150, 27718, 95514, 332578, 1168261, 4136477, 14749992, 52925886, 190973410, 692583902, 2523265494, 9231352260, 33901898722, 124940568222, 461938289518, 1713007181342, 6369928427268, 23747917426918, 88747514693530, 332397792962692, 1247582980566935, 4691740496135919, 17676678143316236, 66714895880626460, 252207367615436780
Offset: 3

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Keywords

Comments

a(n) is also the number of partitions of n(n-1)/2 into n (nonzero) parts, none greater than n-2 [Riordan].

Examples

			1; 1+t+t^2+t^3+t^4+t^5, t^10+t^9+2*t^8+2*t^7+3*t^6+3*t^5+3*t^4+2*t^3+2*t^2+t+1, ...
		

Crossrefs

Programs

  • Maple
    p := proc(n)
    option remember;
    if n = 3 then 1 else
    simplify((1-t^(2*n-4))*(1-t^(2*n-3))*p(n-1)/((1-t^(n-3))*(1-t^n)));
    fi; end;
    for i from 3 to 40 do
    lprint(coeff(expand(p(i)),t,i*(i-3)/2)):
    od:
  • Mathematica
    p[3] = 1; p[n_] := p[n] = (1 - t^(2*n-4))*(1 - t^(2*n-3))*(p[n-1]/((1 - t^(n-3))*(1 - t^n)))// Simplify // Expand; a[n_] := Coefficient[p[n], t, n*(n-3)/2]; Table[a[n], {n, 3, 40}] (* Jean-François Alcover, Aug 01 2013, after Maple *)

Formula

a(n) ~ sqrt(3) * 2^(2*n-3) / (Pi * n^2). - Vaclav Kotesovec, Jan 07 2023

Extensions

Corrected terms and Maple program. - N. J. A. Sloane, May 09 2012

A125032 Triangle read by rows: T(n,k) = number of tournaments with n players which have the k-th score sequence. The score sequences are in the same order as A068029 and start with the empty score sequence.

Original entry on oeis.org

1, 1, 2, 6, 2, 24, 8, 8, 24, 120, 40, 40, 120, 40, 120, 240, 280, 24, 720, 240, 240, 720, 240, 720, 1440, 1680, 144, 240, 80, 720, 1440, 2880, 1680, 1680, 1680, 8640, 2400, 144, 2400, 2640, 5040, 1680, 1680, 5040, 1680, 5040, 10080, 11760, 1008, 1680, 560
Offset: 1

Views

Author

Martin Fuller, Nov 16 2006

Keywords

Comments

The score sequences are sorted by number of players and then lexicographically.
There are A000571(m) score sequences for m players. The sum of all the a(n) for m players is A006125(m)=2^(m(m-1)/2).

Examples

			There are two score sequences with 3 players: [0,1,2] from 6 tournaments and [1,1,1] from 2 tournaments. These score sequences come 4th and 5th respectively, so a(4)=6 and a(5)=2.
		

Crossrefs

Cf. A000571, A006125, A068029, A125031 (number of highest scorers), A123553.
Other sequences that can be calculated using this one: A013976, A125031.

A210726 a(2)=1, a(3)=2; thereafter a(n) = 2a(n-1)-a(n-2)+A046919(n).

Original entry on oeis.org

1, 2, 4, 9, 22, 59, 169, 506, 1577, 5078, 16729, 56098, 190981, 658442, 2294164, 8066363, 28588554, 102036631, 366458118, 1323463507, 4803734390, 17515357533, 64128879398, 235682969485, 869175349090, 3215674910037, 11932102898252, 44396448313385, 165608308422048, 619217961493403, 2320410595131693, 8713343724905902, 32782954997996347, 123567462151713252, 466559336920866937, 1764469819249171154
Offset: 2

Views

Author

N. J. A. Sloane, May 09 2012

Keywords

Comments

According to Riordan (1968), this is the number of possible score sequences in a tournament with n nodes, but the latter is given by A000571, which is a different sequence.

Crossrefs

Cf. A046919.
Showing 1-10 of 21 results. Next