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Search: a172609 -id:a172609
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De Bruijn's triangle, T(m,n) = (m*n)!/(n!^m) read by downward antidiagonals.
+10
24
1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 6, 6, 1, 1, 1, 20, 90, 24, 1, 1, 1, 70, 1680, 2520, 120, 1, 1, 1, 252, 34650, 369600, 113400, 720, 1, 1, 1, 924, 756756, 63063000, 168168000, 7484400, 5040, 1
OFFSET
0,9
COMMENTS
From Tilman Piesk, Oct 28 2014: (Start)
Number of permutations of a multiset that contains m different elements n times. These multisets have the signatures A249543(m,n-1) for m>=1 and n>=2.
In an m-dimensional Pascal tensor (the generalization of a symmetric Pascal matrix) P(x1,...,xn) = (x1+...+xn)!/(x1!*...*xn!), so the main diagonal of an m-dimensional Pascal tensor is D(n) = (m*n)!/(n!^m). These diagonals are the rows of this array (with m>0), which begins like this:
m\n:0 1 2 3 4 5
0: 1 1 1 1 1 1 ... A000012;
1: 1 1 1 1 1 1 ... A000012;
2: 1 2 6 20 70 252 ... A000984;
3: 1 6 90 1680 34650 756756 ... A006480;
4: 1 24 2520 369600 63063000 11732745024 ... A008977;
5: 1 120 113400 168168000 305540235000 623360743125120 ... A008978;
6: 1 720 7484400 137225088000 3246670537110000 88832646059788350720 ... A008979;
with columns: A000142 (n=1), A000680 (n=2), A014606 (n=3), A014608 (n=4), A014609 (n=5).
A089759 is the transpose of this matrix. A034841 is its diagonal. A141906 is its lower triangle. A120666 is the upper triangle of this matrix with indices starting from 1. A248827 are the diagonal sums (or the row sums of the triangle).
(End)
LINKS
T. Chappell, A. Lascoux, S. Ole Warnaar, and W. Zudilin, Logarithmic and complex constant term identities, arXiv:1112.3130 [math.CO], 2012.
FORMULA
T(m,n) = (m*n)!/(n!)^m.
A060540(m,n) = T(m,n)/m! . - R. J. Mathar, Jun 21 2023
EXAMPLE
T(3,5) = (3*5)!/(5!^3) = 756756 = A014609(3) = A006480(5) is the number of permutations of a multiset that contains 3 different elements 5 times, e.g., {1,1,1,1,1,2,2,2,2,2,3,3,3,3,3}.
MATHEMATICA
T[n_, k_]:= (k*n)!/(n!)^k; Table[T[n, k-n], {k, 9}, {n, 0, k-1}]//Flatten
PROG
(Magma) [Factorial(k*(n-k))/(Factorial(n-k))^k: k in [0..n], n in [0..10]]; // G. C. Greubel, Dec 26 2022
(SageMath)
def A187783(n, k): return gamma(k*(n-k)+1)/(factorial(n-k))^k
flatten([[A187783(n, k) for k in range(n+1)] for n in range(11)]) # G. C. Greubel, Dec 26 2022
CROSSREFS
Cf. A089759 (transposed), A141906 (subtriangle), A120666 (subtriangle transposed), A060538 (1st row/colmn removed).
Main diagonal gives: A034841.
Row sums of the triangle: A248827.
KEYWORD
nonn,tabl,easy
AUTHOR
Robert G. Wilson v, Jan 05 2013
EXTENSIONS
Row m=0 prepended by Tilman Piesk, Oct 28 2014
STATUS
approved
Number of permutations of 8 copies of 1..n with all adjacent differences <= 1 in absolute value.
+10
2
1, 1, 12870, 6077196, 5650739930, 3772321496064, 2514046004253110, 1570273521448103668, 951645881858020642746, 560523113474283819256640, 323221203836407773725200718, 183122229346363470922528553652, 102256611847518844993947706000234
OFFSET
0,3
COMMENTS
a(n) = (8n)!/40320^n = A172609(n) for n<=2.
LINKS
CROSSREFS
Column k=8 of A331562.
Cf. A172609.
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Jan 21 2020
Terms a(7) and beyond from Andrew Howroyd, May 15 2020
STATUS
approved
Number of sequences with 8 copies each of 1,2,...,n avoiding the pattern 12...n.
+10
2
0, 0, 1, 15168751, 1020149742404727, 285867869484243410805931, 276745258345325814650980975177139, 789007694236868030155290867470985247486401, 5841526335200139692050292842849347521755651331941759, 101741646114927245552012617872560516024563394870390766150081895
OFFSET
0,4
LINKS
FORMULA
a(n) = A172609(n) - A268851(n).
CROSSREFS
Column k=8 of A269129.
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Feb 19 2016
STATUS
approved
Number of permutations of 8 copies of 1..n with all adjacent differences <= 2 in absolute value.
+10
0
1, 1, 12870, 9465511770, 580132098966420, 19840440079542390102, 1061489454895820193068774
OFFSET
0,3
COMMENTS
a(n) = (8n)!/40320^n for n<=3.
CROSSREFS
Cf. A172609.
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
STATUS
approved
Number of permutations of 8 copies of 1..n with all adjacent differences <= 3 in absolute value.
+10
0
1, 1, 12870, 9465511770, 99561092450391000, 151158246783053570131500, 91756879673807945288868127380
OFFSET
0,3
COMMENTS
a(n) = (8n)!/40320^n for n<=4.
CROSSREFS
Cf. A172609.
KEYWORD
nonn
AUTHOR
R. H. Hardin, May 06 2010
STATUS
approved

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