OFFSET
0,8
COMMENTS
At least one block length occurs exactly k times, and all block lengths occur at most k times.
LINKS
Alois P. Heinz, Rows n = 0..140, flattened
Wikipedia, Partition of a set
EXAMPLE
T(4,1) = 5: 1234, 123|4, 124|3, 134|2, 1|234.
T(4,2) = 9: 12|34, 12|3|4, 13|24, 13|2|4, 14|23, 1|23|4, 14|2|3, 1|24|3, 1|2|34.
T(4,4) = 1: 1|2|3|4.
Triangle T(n,k) begins:
1;
0, 1;
0, 1, 1;
0, 4, 0, 1;
0, 5, 9, 0, 1;
0, 16, 25, 10, 0, 1;
0, 82, 70, 35, 15, 0, 1;
0, 169, 406, 245, 35, 21, 0, 1;
0, 541, 2093, 1036, 385, 56, 28, 0, 1;
0, 2272, 10935, 4984, 2331, 504, 84, 36, 0, 1;
0, 17966, 41961, 37990, 13335, 3717, 840, 120, 45, 0, 1;
...
MAPLE
with(combinat):
b:= proc(n, i, k) option remember; `if`(n=0, 1,
`if`(i<1, 0, add(multinomial(n, n-i*j, i$j)
*b(n-i*j, i-1, k)/j!, j=0..min(k, n/i))))
end:
T:= (n, k)-> b(n$2, k)-`if`(k=0, 0, b(n$2, k-1)):
seq(seq(T(n, k), k=0..n), n=0..12);
MATHEMATICA
multinomial[n_, k_List] := n!/Times @@ (k!); b[n_, i_, k_] := b[n, i, k] = If[n==0, 1, If[i<1, 0, Sum[multinomial[n, Join[{n-i*j}, Array[i&, j]]] * b[n - i*j, i - 1, k]/j!, {j, 0, Min[k, n/i]}]]]; T[n_, k_] := b[n, n, k] - If[k == 0, 0, b[n, n, k - 1]]; Table[T[n, k], {n, 0, 12}, {k, 0, n}] // Flatten (* Jean-François Alcover, Jan 06 2017, after Alois P. Heinz *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Alois P. Heinz, Apr 07 2016
STATUS
approved