OFFSET
0,9
LINKS
Alois P. Heinz, Antidiagonals n = 0..60, flattened
J.-M. Sixdeniers, K. A. Penson and A. I. Solomon, Extended Bell and Stirling Numbers From Hypergeometric Exponentiation, J. Integer Seqs. Vol. 4 (2001), #01.1.4.
Wikipedia, Partition of a set
EXAMPLE
A(2,2) = 3: 1234, 12|34, 14|23.
A(2,3) = 5: 123456, 123|456, 126|345, 135|246, 156|234.
A(2,4) = 9: 12345678, 1234|5678, 1238|4567, 1247|3568, 1278|3456, 1346|2578, 1368|2457, 1467|2358, 1678|2345.
A(3,2) = 16: 123456, 1234|56, 1236|45, 1245|36, 1256|34, 12|3456, 12|34|56, 12|36|45, 1346|25, 1456|23, 14|2356, 14|23|56, 16|2345, 16|23|45, 14|25|36, 16|25|34.
Square array A(n,k) begins:
1, 1, 1, 1, 1, 1, 1, ...
1, 1, 1, 1, 1, 1, 1, ...
1, 2, 3, 5, 9, 17, 33, ...
1, 5, 16, 64, 298, 1540, 8506, ...
1, 15, 131, 1613, 25097, 461105, 9483041, ...
1, 52, 1496, 69026, 4383626, 350813126, 33056715626, ...
1, 203, 22482, 4566992, 1394519922, 573843627152, 293327384637282, ...
MAPLE
A:= proc(n, k) option remember; `if`(k*n=0, 1, add(
binomial(n, j)^k*(n-j)*A(j, k), j=0..n-1)/n)
end:
seq(seq(A(n, d-n), n=0..d), d=0..12);
MATHEMATICA
A[n_, k_] := A[n, k] = If[k*n == 0, 1, Sum[Binomial[n, j]^k*(n-j)*A[j, k], {j, 0, n-1}]/n]; Table[A[n, d-n], {d, 0, 12}, {n, 0, d}] // Flatten (* Jean-François Alcover, Jan 17 2017, translated from Maple *)
CROSSREFS
KEYWORD
nonn,tabl
AUTHOR
Alois P. Heinz, Jul 14 2016
STATUS
approved