A157400 A partition product with biggest-part statistic of Stirling_1 type (with parameter k = -2) as well as of Stirling_2 type (with parameter k = -2), (triangle read by rows).
1, 1, 2, 1, 6, 6, 1, 24, 24, 24, 1, 80, 180, 120, 120, 1, 330, 1200, 1080, 720, 720, 1, 1302, 7770, 10920, 7560, 5040, 5040, 1, 5936, 57456, 102480, 87360, 60480, 40320, 40320, 1, 26784, 438984, 970704, 1103760, 786240, 544320, 362880, 362880
Offset: 1
Examples
Triangle starts: 1; 1, 2; 1, 6, 6; 1, 24, 24, 24; 1, 80, 180, 120, 120; 1, 330, 1200, 1080, 720, 720; ...
Links
- Peter Luschny, Counting with Partitions.
- Peter Luschny, Generalized Stirling_1 Triangles.
- Peter Luschny, Generalized Stirling_2 Triangles.
Crossrefs
Programs
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Maple
egf:= k-> exp((x^(k+1)-x)/(x-1))-exp((x^k-x)/(x-1)): T:= (n, k)-> n!*coeff(series(egf(k), x, n+1), x, n): seq(seq(T(n, k), k=1..n), n=1..10); # Alois P. Heinz, Oct 10 2015
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Mathematica
egf[k_] := Exp[(x^(k+1)-x)/(x-1)] - Exp[(x^k-x)/(x-1)]; T[n_, k_] := n! * SeriesCoefficient[egf[k], {x, 0, n}]; Table[Table[T[n, k], {k, 1, n}], {n, 1, 10}] // Flatten (* Jean-François Alcover, Oct 11 2015, after Alois P. Heinz *)
Formula
T(n,0) = [n = 0] (Iverson notation) and for n > 0 and 1 <= m <= n.
T(n,m) = Sum_{a} M(a)|f^a| where a = a_1,...,a_n such that
1*a_1 + 2*a_2 + ... + n*a_n = n and max{a_i} = m, M(a) = n!/(a_1!*..*a_n!),
f^a = (f_1/1!)^a_1*..*(f_n/n!)^a_n and f_n = Product_{j=0..n-1} (-j-1)
OR f_n = Product_{j=0..n-2} (j-n) since both have the same absolute value n!.
E.g.f. of column k: exp((x^(k+1)-x)/(x-1))-exp((x^k-x)/(x-1)). - Alois P. Heinz, Oct 10 2015
Comments