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 1-6 of 6 results.

A019575 Place n distinguishable balls in n boxes (in n^n ways); let T(n,k) = number of ways that the maximum in any box is k, for 1 <= k <= n; sequence gives triangle of numbers T(n,k).

Original entry on oeis.org

1, 2, 2, 6, 18, 3, 24, 180, 48, 4, 120, 2100, 800, 100, 5, 720, 28800, 14700, 2250, 180, 6, 5040, 458640, 301350, 52920, 5292, 294, 7, 40320, 8361360, 6867840, 1342600, 153664, 10976, 448, 8, 362880, 172141200, 172872000, 36991080, 4644864, 387072, 20736, 648, 9
Offset: 1

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com)

Keywords

Comments

T(n,k) is the number of endofunctions on [n] such that the maximal cardinality of the nonempty preimages equals k. - Alois P. Heinz, Jul 31 2014

Examples

			Triangle begins:
       1;
       2,         2;
       6,        18,         3;
      24,       180,        48,        4;
     120,      2100,       800,      100,       5;
     720,     28800,     14700,     2250,     180,      6;
    5040,    458640,    301350,    52920,    5292,    294,     7;
   40320,   8361360,   6867840,  1342600,  153664,  10976,   448,   8;
  362880, 172141200, 172872000, 36991080, 4644864, 387072, 20736, 648, 9;
  ...
		

Crossrefs

Cf. A019576. See A180281 for the case when the balls are indistinguishable.
Rows sums give A000312.
Cf. A245687.

Programs

  • Maple
    b:= proc(n, i, k) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(b(n-j, i-1, k)/j!, j=0..min(k, n))))
        end:
    T:= (n, k)-> n!* (b(n$2, k) -b(n$2, k-1)):
    seq(seq(T(n, k), k=1..n), n=1..12);  # Alois P. Heinz, Jul 29 2014
  • Mathematica
    f[0, , b] := Boole[b == 0]; f[n_, k_, b_] := f[n, k, b] = Sum[ Binomial[b, i]*f[n - 1, k, b - i], {i, 0, Min[k, b]}]; t[n_, k_] := f[n, k, n] - f[n, k - 1, n]; Flatten[ Table[ t[n, k], {n, 1, 9}, {k, 1, n}]] (* Jean-François Alcover, Mar 09 2012, after Robert Gerbicz *)
  • PARI
    /*setup memoization table for args <= M. Could be done dynamically inside f() */
    M=10;F=vector(M,i,vector(M,i,vector(M)));
    f(n,k,b)={ (!n||!b||!k) & return(!b); F[n][k][b] & return(F[n][k][b]);
    F[n][k][b]=sum(i=0,min(k,b),binomial(b,i)*f(n-1,k,b-i)) }
    T(n,k)=f(n,k,n)-f(n,k-1,n)
    for(n=1,9,print(vector(n,k,T(n,k))))
    \\ M. F. Hasler, Aug 19 2010; Based on Robert Gerbicz's code I suggest the following (very naively) memoized version of "f"

Formula

A019575(x, z) = Sum ( A049009(p)) where x = A036042(p), z = A049085(p) - Alford Arnold.
From Robert Gerbicz, Aug 19 2010: (Start)
Let f(n,k,b) = number of ways to place b balls to n boxes, where the max in any box is not larger than k. Then T(n,k) = f(n,k,n) - f(n,k-1,n). We have:
f(n, k, b) = if(n=0, if(b=0, 1, 0), Sum_{i=0..min(k, b)} binomial(b, i)*f(n-1, k, b-i)).
T(n,k) = f(n,k,n) - f(n,k-1,n). (End)

Extensions

Edited by N. J. A. Sloane, Sep 06 2010

A019577 Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1<=k<=n; sequence gives f(n,2)/n.

Original entry on oeis.org

0, 1, 6, 45, 420, 4800, 65520, 1045170, 19126800, 395448480, 9120988800, 232248416400, 6471820555200, 195912193276800, 6402199349145600, 224636583525354000, 8423131243022496000, 336138596955120960000, 14224375944427993344000, 636224790017466730080000
Offset: 1

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com), N. J. A. Sloane

Keywords

Crossrefs

Cf. A019576.

Formula

Sum n! (n-1)! / ( 2^d (n-2d)! d! d! ), d=1..[ n/2 ].

A019579 Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1 <= k <= n; sequence gives f(n,n-2)/n.

Original entry on oeis.org

2, 45, 160, 375, 756, 1372, 2304, 3645, 5500, 7986, 11232, 15379, 20580, 27000, 34816, 44217, 55404, 68590, 84000, 101871, 122452, 146004, 172800, 203125, 237276, 275562, 318304, 365835, 418500, 476656, 540672, 610929, 687820, 771750, 863136, 962407
Offset: 3

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com), N. J. A. Sloane

Keywords

Crossrefs

Cf. A019576.

Programs

  • Mathematica
    CoefficientList[Series[-(9 x^6 - 35 x^5 + 41 x^4 + 5 x^3 - 45 x^2 + 35 x + 2)/(x - 1)^5, {x, 0, 50}], x] (* Vincenzo Librandi, Oct 16 2013 *)
    LinearRecurrence[{5,-10,10,-5,1},{2,45,160,375,756,1372,2304},40] (* Harvey P. Dale, Dec 18 2020 *)

Formula

a(n) = n*(n-1)^3/2, n >= 5.
G.f.: -x^3*(9*x^6 - 35*x^5 + 41*x^4 + 5*x^3 - 45*x^2 + 35*x + 2) / (x-1)^5. [Colin Barker, Jan 11 2013]
a(n) = 5*a(n-1)-10*a(n-2)+10*a(n-3)-5*a(n-4)+a(n-5). - Wesley Ivan Hurt, Dec 27 2021

Extensions

More terms from Vincenzo Librandi, Oct 16 2013

A019581 Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1<=k<=n; sequence gives f(n,2).

Original entry on oeis.org

0, 2, 18, 180, 2100, 28800, 458640, 8361360, 172141200, 3954484800, 100330876800, 2786980996800, 84133667217600, 2742770705875200, 96032990237184000, 3594185336405664000, 143193231131382432000, 6050494745192177280000, 270263142944131873536000
Offset: 1

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com), N. J. A. Sloane

Keywords

Crossrefs

Cf. A019576.
Column k=2 of A019575. - Alois P. Heinz, Jul 29 2014

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
          add(b(n-j, i-1)/j!, j=0..min(2, n))))
        end:
    a:= n-> n! *(b(n$2) -1):
    seq(a(n), n=1..30);  # Alois P. Heinz, Jul 29 2014
  • Mathematica
    a[n_] := n! (Hypergeometric2F1[1/2 - n/2, -n/2, 1, 2] - 1); Array[a, 30] (* Jean-François Alcover, Feb 18 2016 *)
  • PARI
    a(n) = sum(d=1, n\2, n!^2 / (2^d * (n-2*d)! * d!^2)); \\ Michel Marcus, Aug 13 2013

Formula

a(n) = sum(d=1..floor(n/2), n!^2 / ( 2^d * (n-2*d)! * d! * d! ) ).

A019578 Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1<=k<=n; sequence gives f(n,3)/n.

Original entry on oeis.org

1, 12, 160, 2450, 43050, 858480, 19208000, 477237600, 13049190000, 389642022000, 12620614406400, 440871877446000, 16525943429595600, 661779275661504000, 28199857953915648000, 1274233240573028736000, 60863881753459328544000
Offset: 3

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com)

Keywords

Crossrefs

Cf. A019576.

Extensions

More terms from Sean A. Irvine, Mar 27 2019

A019580 Place n distinguishable balls in n boxes (in n^n ways); let f(n,k) = number of ways that max in any box is k, for 1<=k<=n; sequence gives f(n,4)/n.

Original entry on oeis.org

1, 20, 375, 7560, 167825, 4110120, 110602800, 3252075750, 103881924300, 3585467886000, 133052005386300, 5284678706307000, 223761183682286250, 10063370411081988000, 479152851159102120000, 24082014064135799772000
Offset: 4

Views

Author

Lee Corbin (lcorbin(AT)tsoft.com)

Keywords

Crossrefs

Cf. A019576.

Extensions

More terms from Sean A. Irvine, Mar 27 2019
Showing 1-6 of 6 results.