A178300 Triangle T(n,k) = binomial(n+k-1,n) read by rows, 1 <= k <= n.

1, 1, 3, 1, 4, 10, 1, 5, 15, 35, 1, 6, 21, 56, 126, 1, 7, 28, 84, 210, 462, 1, 8, 36, 120, 330, 792, 1716, 1, 9, 45, 165, 495, 1287, 3003, 6435, 1, 10, 55, 220, 715, 2002, 5005, 11440, 24310, 1, 11, 66, 286, 1001, 3003, 8008, 19448, 43758, 92378, 1, 12, 78, 364, 1365, 4368, 12376, 31824, 75582, 167960, 352716, 1, 13, 91, 455, 1820, 6188, 18564, 50388, 125970, 293930, 646646, 1352078

Offset

1,3

Comments

Obtained from A176992 by reversing entries in each row, from A092392 by removing the left column and reversing entries in each row, or from A100100 by removing the first two columns and reversing entries in each row.

Also T(n,k) = count of degree k monomials in the Monomial symmetric polynomials m(mu,k) summed over all partitions mu of n.

T(n,k) is the number of ways to put n indistinguishable balls into k distinguishable boxes. - Dennis P. Walsh, Apr 11 2012

T(n,k) is the number of compositions of n into k parts if zeros are allowed as parts. - L. Edson Jeffery, Jul 23 2014

T(n,k) is the number of compositions (ordered partitions) of n+k into exactly k parts. - Juergen Will, Jan 23 2016

T(n,k) is the number of binary strings with exactly n zeros and k-1 ones. - Dennis P. Walsh, Apr 09 2016

T(n,k) is the number of functions f:[k-1]->[n+1] that are nondecreasing. There is a unique correspondence between such a function and a binary string with exactly n zeros and k-1 ones. Given a string, let the corresponding function f be defined by f(i)=1 + (the number of zeros in the string that precede the i-th one in the string) for i=1,..,k-1. - Dennis P. Walsh, Apr 09 2016

Links

Table of n, a(n) for n=1..78.

P. A. MacMahon, Memoir on the Theory of the Compositions of Numbers, Phil. Trans. Royal Soc. London A, 184 (1893), 835-901.

Ch. Stover and E. W. Weisstein, Composition. From MathWorld - A Wolfram Web Resource.

Wikipedia, Symmetric Polynomials

Formula

T(n,k) = A046899(n,k-1) = A038675(n,k)/A008292(n,k).

T(n,1) = 1.

T(n,2) = n+1.

T(n,3) = A000217(n+1).

T(n,4) = A000292(n+1).

T(n,5) = A000332(n+4).

T(n,n) = A001700(n-1) = A088218(n). - Dennis P. Walsh, Apr 10 2012

Example

Triangle begins
  1;
  1,    3;
  1,    4,   10;
  1,    5,   15,   35;
  1,    6,   21,   56,  126;
  1,    7,   28,   84,  210,  462;
  1,    8,   36,  120,  330,  792, 1716;
T(3,3)=10 since there are 10 ways to put 3 identical balls into 3 distinguishable boxes, namely, (OOO)()(), ()(OOO)(), ()()(OOO), (OO)(O)(), (OO)()(O), (O)(OO)(), ()(OO)(O), (O)()(OO), ()(O)(OO), and (O)(O)(O). - Dennis P. Walsh, Apr 11 2012
For example, T(3,3)=10 since there are ten functions f:[2]->[4] that are nondecreasing, namely, <f(1),f(2)> = <1,1> or <1,2> or <1,3> or <1,4> or <2,2> or <2,3> or <2,4> or <3,3> or <3,4> or <4,4>. - Dennis P. Walsh, Apr 09 2016

Maple

seq(seq(binomial(n+k-1, n), k=1..n), n=1..15); # Dennis P. Walsh, Apr 11 2012

Mathematica

m[par_?PartitionQ, v_] := Block[{le = Length[par], it }, If[le > v, Return[0]]; it = Permutations[PadRight[par, v]]; Tr[ Apply[Times, Table[Subscript[x, j], {j, v}]^# & /@ it, {1}]]];
Table[Tr[(m[#, k] & /@ Partitions[l]) /. Subscript[x, _] -> 1], {l, 11}, {k, l}](* Wouter Meeussen, Mar 11 2012 *)
Quiet[Needs["Combinatorica`"], All]; Grid[Table[Length[Combinatorica`Compositions[n, k]], {n, 10}, {k, n}]] (* L. Edson Jeffery, Jul 24 2014 *)
t[n_, k_] := Binomial[n + k - 1, n]; Table[ t[n, k], {n, 10}, {k, n}] // Flatten (* Robert G. Wilson v, Jul 24 2014 *)

Prog

(Magma) (* As triangle *) [[Binomial(n+k-1, n): k in [1..n]]: n in [1.. 15]]; // Vincenzo Librandi, Jan 24 2016

Crossrefs

Cf. A000142, A000312, A007318, A001791 (row sums), A209664-A209673.

Cf. A000217, A000292, A000332, A001700, A008292, A038675, A046899, A088218.

Cf. A176992, A092392, A100100.

Sequence in context: A193792 A190179 A025116 * A081720 A137405 A322456

Adjacent sequences: A178297 A178298 A178299 * A178301 A178302 A178303

Keyword

easy,nonn,tabl

Author

Alford Arnold, May 24 2010

Status

approved