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.

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A309992 Triangle T(n,k) whose n-th row lists in increasing order the multinomial coefficients M(n;lambda), where lambda ranges over all partitions of n into distinct parts; n >= 0, 1 <= k <= A000009(n), read by rows.

Original entry on oeis.org

1, 1, 1, 1, 3, 1, 4, 1, 5, 10, 1, 6, 15, 60, 1, 7, 21, 35, 105, 1, 8, 28, 56, 168, 280, 1, 9, 36, 84, 126, 252, 504, 1260, 1, 10, 45, 120, 210, 360, 840, 1260, 2520, 12600, 1, 11, 55, 165, 330, 462, 495, 1320, 2310, 4620, 6930, 27720
Offset: 0

Views

Author

Alois P. Heinz, Aug 26 2019

Keywords

Comments

First row with repeated terms is row 15, see also A309999: 1365 = M(15;11,4) = M(15;12,2,1) and 30030 = M(15;9,5,1) = M(15;10,3,2).

Examples

			For n = 5 there are 3 partitions of 5 into distinct parts: [5], [4,1], [3,2].  So row 5 contains M(5;5) = 1, M(5;4,1) = 5 and M(5;3,2) = 10.
Triangle T(n,k) begins:
  1;
  1;
  1;
  1,  3;
  1,  4;
  1,  5, 10;
  1,  6, 15,  60;
  1,  7, 21,  35, 105;
  1,  8, 28,  56, 168, 280;
  1,  9, 36,  84, 126, 252, 504, 1260;
  1, 10, 45, 120, 210, 360, 840, 1260, 2520, 12600;
  1, 11, 55, 165, 330, 462, 495, 1320, 2310,  4620, 6930, 27720;
  ...
		

Crossrefs

Columns k=1-3 give: A000012, A000027 (for n>=3), A000217(n-1) (for n>=5).
Row sums give A007837.
Rightmost terms of rows give A290517.

Programs

  • Maple
    g:= proc(n, i) option remember; `if`(i*(i+1)/2binomial(n, i)*x, g(n-i, min(n-i, i-1)))[], g(n, i-1)[]]))
        end:
    T:= n-> sort(g(n$2))[]:
    seq(T(n), n=0..14);
  • Mathematica
    g[n_, i_] := g[n, i] = If[i(i+1)/2 < n, {}, If[n == 0, {1}, Join[ Binomial[n, i] # & /@ g[n-i, Min[n-i, i-1]], g[n, i-1]]]];
    T[n_] := Sort[g[n, n]];
    T /@ Range[0, 14] // Flatten (* Jean-François Alcover, Jan 27 2021, after Alois P. Heinz *)

A290518 Minimum value of Product_{i in lambda} i!, where lambda ranges over all partitions of n into distinct parts.

Original entry on oeis.org

1, 1, 2, 2, 6, 12, 12, 48, 144, 288, 288, 1440, 5760, 17280, 34560, 34560, 207360, 1036800, 4147200, 12441600, 24883200, 24883200, 174182400, 1045094400, 5225472000, 20901888000, 62705664000, 125411328000, 125411328000, 1003290624000, 7023034368000
Offset: 0

Views

Author

Alois P. Heinz, Aug 04 2017

Keywords

Examples

			a(10) = 288 = (4! * 3! * 2! * 1!) is the value for partition [4,3,2,1]. All other partitions of 10 into distinct parts give larger values: [5,3,2]-> 1440, [5,4,1]-> 2880, [6,3,1]-> 4320, [6,4]-> 17280, [7,2,1]-> 10080, [7,3]-> 30240, [8,2]-> 80640, [9,1]-> 362880, [10]-> 3628800.
		

Crossrefs

Programs

  • Maple
    b:= proc(n, i) option remember; `if`(n>i*(i+1)/2, infinity,
         `if`(n=0, 1, min(b(n, i-1), b(n-i, min(n-i, i-1))*i!)))
        end:
    a:= n-> b(n$2):
    seq(a(n), n=0..30);
    # second Maple program:
    a:= proc(n) option remember; `if`(n=0, 1, a(n-1)*
          (t-> t*(t+3)/2-n+2)(floor(sqrt(8*n-7)/2-1/2)))
        end:
    seq(a(n), n=0..30);  # Alois P. Heinz, Aug 05 2017
  • Mathematica
    b[n_, i_]:=b[n, i]=If[n>i*(i + 1)/2, Infinity, If[n==0, 1, Min[b[n, i - 1], b[n - i, Min[n - i, i - 1]]*i!]]];  Table[b[n, n], {n, 0, 30}] (* Indranil Ghosh, Aug 05 2017, after Maple *)

Formula

a(n) = A000142(n) / A290517(n).
a(0) = 1, a(n) = a(n-1) * A004736(n) for n>0.
a(n) = a(n-1) iff n in { A000217 } \ { 0 }.
Showing 1-2 of 2 results.