OFFSET
0,6
COMMENTS
The Fuss-Catalan triangle of order m is a regular, (0, 0)-based table recursively defined as follows: Set row(0) = [1] and row(1) = [0, 1]. Now assume row(n-1) already constructed and duplicate the last element of row(n-1). Next apply the cumulative sum m times to this list to get row(n). Here m = 1. (See the Python program for a reference implementation.)
This definition also includes the classical Fuss-Catalan numbers, since T(n, n) = A000108(n), or row 2 in A355262. For m = 2 see A355172 and for m = 3 A355174. More generally, for n >= 1 all Fuss-Catalan sequences (A355262(n, k), k >= 0) are the main diagonals of the Fuss-Catalan triangles of order n - 1.
FORMULA
The general formula for the Fuss-Catalan triangles is, for m >= 0 and 0 <= k <= n:
FCT(n, k, m) = (m*(n - k) + m + 1)*(m*n + k - 1)!/((m*n + 1)!*(k - 1)!)) for k > 0 and FCT(n, 0, m) = 0^n. The case considered here is T(n, k) = FCT(n, k, 1).
T(n, k) = (n - k + 2)*(n + k - 1)!/((n + 1)!*(k - 1)!) for k > 0; T(n, 0) = 0^n.
The g.f. of row n of the FC-triangle of order m is 0^n + (x - (m + 1)*x^2) / (1 - x)^(m*n + 2), thus:
T(n, k) = [x^k] (0^n + (x - 2*x^2)/(1 - x)^(n + 2)).
EXAMPLE
Table T(n, k) begins:
[0] [1]
[1] [0, 1]
[2] [0, 1, 2]
[3] [0, 1, 3, 5]
[4] [0, 1, 4, 9, 14]
[5] [0, 1, 5, 14, 28, 42]
[6] [0, 1, 6, 20, 48, 90, 132]
[7] [0, 1, 7, 27, 75, 165, 297, 429]
[8] [0, 1, 8, 35, 110, 275, 572, 1001, 1430]
[9] [0, 1, 9, 44, 154, 429, 1001, 2002, 3432, 4862]
.
Seen as an array reading the diagonals starting from the main diagonal:
[0] 1, 1, 2, 5, 14, 42, 132, 429, 1430, 4862, 16796, ... A000108
[1] 0, 1, 3, 9, 28, 90, 297, 1001, 3432, 11934, 41990, ... A000245
[2] 0, 1, 4, 14, 48, 165, 572, 2002, 7072, 25194, 90440, ... A099376
[3] 0, 1, 5, 20, 75, 275, 1001, 3640, 13260, 48450, 177650, ... A115144
[4] 0, 1, 6, 27, 110, 429, 1638, 6188, 23256, 87210, 326876, ... A115145
[5] 0, 1, 7, 35, 154, 637, 2548, 9996, 38760, 149226, 572033, ... A000588
[6] 0, 1, 8, 44, 208, 910, 3808, 15504, 62016, 245157, 961400, ... A115147
[7] 0, 1, 9, 54, 273, 1260, 5508, 23256, 95931, 389367, 1562275, ... A115148
PROG
(Python)
from functools import cache
from itertools import accumulate
@cache
def Trow(n: int) -> list[int]:
if n == 0: return [1]
if n == 1: return [0, 1]
row = Trow(n - 1) + [Trow(n - 1)[n - 1]]
return list(accumulate(row))
for n in range(11): print(Trow(n))
CROSSREFS
A000108 (main diagonal), A000245 (subdiagonal), A002057 (diagonal 2), A000344 (diagonal 3), A000027 (column 2), A000096 (column 3), A071724 (row sums), A000958 (alternating row sums), A262394 (main diagonal of array).
KEYWORD
nonn,tabl
AUTHOR
Peter Luschny, Jun 25 2022
STATUS
approved