OFFSET
1,2
COMMENTS
Interpolates between A000670 and factorials.
From Thomas Scheuerle, Apr 25 2022: (Start)
Number of preferential arrangements of n labeled elements when at least k ranks are required.
This sequence starts for k and n with offset 1. If it would start with k = 0, we would observe in column k = 0 an exact copy of column k = 1 with a preceding one at n = 0, k = 0. The difference between 0 ranks and one rank (all in the same rank) is only for n = 0 where k = 0 allows zero-filled ranks as an valid arrangement, too. (End)
FORMULA
E.g.f. for m-th column: (exp(x)-1)^m/(2-exp(x)). - Vladeta Jovovic, Sep 14 2003
T(n, k) = Sum_{m = k..n} A090582(n + 1, m + 1).
From Thomas Scheuerle, Apr 25 2022: (Start)
Sum_{k = 0..n} T(n, k) = A005649(n). Column k = 0 is not part of data.
Sum_{k = 1..n} T(n, k) = A069321(n).
T(n, 0) = A000670(n). Column k = 0 is not part of data.
T(n, 1) = A000670(n), for n > 0.
T(n, 2) = A052875(n).
T(n, 3) = A102232(n).
T(n, n) = n! = A000142. (End)
EXAMPLE
Triangle begins with T(n,k):
k= 1, 2, 3, 4, 5
n=1 1
n=2 3, 2
n=3 13, 12, 6
n=4 75, 74, 60, 24
n=5 541, 540, 510, 360, 120
...
From Thomas Scheuerle, Apr 25 2022: (Start)
If we would add n = 0, k = 0 to the data of this sequence:
k= 0, 1, 2,
n=0 1
n=1 1, 1
n=2 3, 3, 2
...
T(n, 3) with 3 preceding zeros is: 0,0,0,6,60,510,4620,...
This sequence has the e.g.f.: (e^x-1)^3/(2-e^x).
.
13 arrangements for n = 3 and k = 1 (one rank required):
1,2,3 1,2|3 2,3|1 1,3|2 1|2,3 2|1,3 3|1,2 1|2|3 1|3|2 2|1|3 2|3|1 3|1|2 3|2|1
12 arrangements for n = 3 and k = 2 (two ranks required):
1,2|3 2,3|1 1,3|2 1|2,3 2|1,3 3|1,2 1|2|3 1|3|2 2|1|3 2|3|1 3|1|2 3|2|1
6 arrangements for n = 3 and k = 3 (three ranks required):
1|2|3 1|3|2 2|1|3 2|3|1 3|1|2 3|2|1
. (End)
MAPLE
T := (n, k)->sum(i!*Stirling2(n, i), i=k..n): seq(seq(T(n, k), k=1..n), n=1..10);
PROG
(PARI) row(n) = vector(n, k, sum(i=k, n, i!*stirling(n, i, 2))); \\ Michel Marcus, Apr 20 2022
CROSSREFS
Mirror image of array in A084417.
KEYWORD
AUTHOR
N. J. A. Sloane, Jun 24 2003
EXTENSIONS
More terms from Emeric Deutsch, May 11 2004
More terms from Michel Marcus, Apr 20 2022
STATUS
approved