A241981 Number T(n,k) of endofunctions on [n] where the largest cycle length equals k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.

1, 0, 1, 0, 3, 1, 0, 16, 9, 2, 0, 125, 93, 32, 6, 0, 1296, 1155, 500, 150, 24, 0, 16807, 17025, 8600, 3240, 864, 120, 0, 262144, 292383, 165690, 72030, 24696, 5880, 720, 0, 4782969, 5752131, 3568768, 1719060, 688128, 215040, 46080, 5040

Offset: 0

Author

Alois P. Heinz, Aug 10 2014

Keywords

• nonn
• tabl

Comments

T(0,0) = 1 by convention.

In general, number of endofunctions on [n] where the largest cycle length equals k is asymptotic to (k*exp(H(k)) - (k-1)*exp(H(k-1))) * n^(n-1), where H(k) is the harmonic number A001008/A002805, k>=1. The multiplicative constant is (for big k) asymptotic to 2*k*exp(gamma), where gamma is the Euler-Mascheroni constant (see A001620 and A073004). - Vaclav Kotesovec, Aug 21 2014

Examples

			Triangle T(n,k) begins:
  1;
  0,      1;
  0,      3,      1;
  0,     16,      9,      2;
  0,    125,     93,     32,     6;
  0,   1296,   1155,    500,   150,    24;
  0,  16807,  17025,   8600,  3240,   864,  120;
  0, 262144, 292383, 165690, 72030, 24696, 5880, 720;
  ...
		

Links

• Alois P. Heinz, Rows n = 0..140, flattened

Crossrefs

Columns k=0-10 give: A000007, A000272(n+1) for n>0, A163951, A246213, A246214, A246215, A246216, A246217, A246218, A246219, A246220.

T(2n,n) gives A241982.

Row sums give A000312.

Main diagonal gives A000142(n-1) for n>0.

Cf. A246049, A243098.

Programs

Maple

with(combinat):
b:= proc(n, i) option remember; `if`(n=0, 1, `if`(i<1, 0,
      add((i-1)!^j*multinomial(n, n-i*j, i$j)/j!*
      b(n-i*j, i-1), j=0..n/i)))
    end:
A:= (n, k)-> add(binomial(n-1, j-1)*n^(n-j)*b(j, min(j, k)), j=0..n):
T:= (n, k)-> A(n, k) -`if`(k=0, 0, A(n, k-1)):
seq(seq(T(n, k), k=0..n), n=0..10);

Mathematica

multinomial[n_, k_List] := n!/Times @@ (k!); b[n_, i_] := b[n, i] = If[n == 0, 1, If[i<1, 0, Sum[(i-1)!^j*multinomial[n, {n-i*j, Sequence @@ Table[i, {j}]}]/j!*b[n-i*j, i-1], {j, 0, n/i}]]]; A[n_, k_] := Sum[Binomial[n-1, j-1]*n^(n-j)*b[j, Min[j, k]], {j, 0, n}]; T[0, 0] = 1; T[n_, k_] := A[n, k] - If[k == 0, 0, A[n, k-1]]; Table[Table[T[n, k], {k, 0, n}], {n, 0, 10}] // Flatten (* Jean-François Alcover, Jan 06 2015, after Alois P. Heinz *)