A275062 Number A(n,k) of permutations p of [n] such that p(i)-i is a multiple of k for all i in [n]; square array A(n,k), n>=0, k>=0, read by antidiagonals.
1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 6, 1, 1, 1, 1, 2, 24, 1, 1, 1, 1, 1, 4, 120, 1, 1, 1, 1, 1, 2, 12, 720, 1, 1, 1, 1, 1, 1, 4, 36, 5040, 1, 1, 1, 1, 1, 1, 2, 8, 144, 40320, 1, 1, 1, 1, 1, 1, 1, 4, 24, 576, 362880, 1, 1, 1, 1, 1, 1, 1, 2, 8, 72, 2880, 3628800, 1
Offset: 0
Examples
A(5,0) = A(5,5) = 1: 12345.
A(5,1) = 5! = 120: all permutations of {1,2,3,4,5}.
A(5,2) = 12: 12345, 12543, 14325, 14523, 32145, 32541, 34125, 34521, 52143, 52341, 54123, 54321.
A(5,3) = 4: 12345, 15342, 42315, 45312.
A(5,4) = 2: 12345, 52341.
A(7,4) = 8: 1234567, 1274563, 1634527, 1674523, 5234167, 5274163, 5634127, 5674123.
Square array A(n,k) begins:
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...
1, 6, 2, 1, 1, 1, 1, 1, 1, 1, 1, ...
1, 24, 4, 2, 1, 1, 1, 1, 1, 1, 1, ...
1, 120, 12, 4, 2, 1, 1, 1, 1, 1, 1, ...
1, 720, 36, 8, 4, 2, 1, 1, 1, 1, 1, ...
1, 5040, 144, 24, 8, 4, 2, 1, 1, 1, 1, ...
1, 40320, 576, 72, 16, 8, 4, 2, 1, 1, 1, ...
1, 362880, 2880, 216, 48, 16, 8, 4, 2, 1, 1, ...
1, 3628800, 14400, 864, 144, 32, 16, 8, 4, 2, 1, ...
Links
- Alois P. Heinz, Antidiagonals n = 0..140, flattened
Crossrefs
Programs
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Maple
A:= (n, k)-> mul(floor((n+i)/k)!, i=0..k-1): seq(seq(A(n, d-n), n=0..d), d=0..14);
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Mathematica
A[n_, k_] := Product[Floor[(n+i)/k]!, {i, 0, k-1}]; Table[A[n, d-n], {d, 0, 14}, {n, 0, d}] // Flatten (* Jean-François Alcover, May 26 2019, from Maple *)
Formula
A(n,k) = Product_{i=0..k-1} floor((n+i)/k)!.
A(k*n,k) = (n!)^k = A225816(k,n).
For k > 0, A(n, k) ~ (2*Pi*n)^((k - 1)/2) * n! / k^(n + k/2). - Vaclav Kotesovec, Oct 02 2018
Comments