A243098
Number T(n,k) of endofunctions on [n] with all cycles of length k; triangle T(n,k), n>=0, 0<=k<=n, read by rows.
Original entry on oeis.org
1, 0, 1, 0, 3, 1, 0, 16, 6, 2, 0, 125, 51, 24, 6, 0, 1296, 560, 300, 120, 24, 0, 16807, 7575, 4360, 2160, 720, 120, 0, 262144, 122052, 73710, 41160, 17640, 5040, 720, 0, 4782969, 2285353, 1430016, 861420, 430080, 161280, 40320, 5040
Offset: 0
Triangle T(n,k) begins:
1;
0, 1;
0, 3, 1;
0, 16, 6, 2;
0, 125, 51, 24, 6;
0, 1296, 560, 300, 120, 24;
0, 16807, 7575, 4360, 2160, 720, 120;
0, 262144, 122052, 73710, 41160, 17640, 5040, 720;
...
Main diagonal gives
A000142(n-1) for n>0.
-
with(combinat):
T:= (n, k)-> `if`(k*n=0, `if`(k+n=0, 1, 0),
add(binomial(n-1, j*k-1)*n^(n-j*k)*(k-1)!^j*
multinomial(j*k, k$j, 0)/j!, j=0..n/k)):
seq(seq(T(n, k), k=0..n), n=0..10);
-
multinomial[n_, k_] := n!/Times @@ (k!); T[n_, k_] := If[k*n==0, If[k+n == 0, 1, 0], Sum[Binomial[n-1, j*k-1]*n^(n-j*k)*(k-1)!^j*multinomial[j*k, Append[Array[k&, j], 0]]/j!, {j, 0, n/k}]]; Table[T[n, k], {n, 0, 10}, {k, 0, n}] // Flatten (* Jean-François Alcover, Feb 19 2017, translated from Maple *)
A057817
Moebius invariant of cographic hyperplane arrangement for complete graph K_n. Also value of Tutte dichromatic polynomial T_G(0,1) for G=K_n. Also alternating sum F_{n,1} - F_{n,2} + F_{n,3} - ..., where F_{n,k} is the number of labeled forests on n nodes with k connected components.
Original entry on oeis.org
1, 0, 1, 6, 51, 560, 7575, 122052, 2285353, 48803904, 1171278945, 31220505800, 915350812299, 29281681800384, 1015074250155511, 37909738774479600, 1517587042234033425, 64830903253553212928, 2944016994706445303937
Offset: 1
Alex Postnikov (apost(AT)math.mit.edu), Nov 06 2000
For n=4, the number of labeled edge-rooted forests on three (= n-1) nodes is 6: There are 3 labeled trees on three nodes. These are the only forests with at least one edge in each connected component. Each tree has 2 edges and each of the two may be marked as the root.
- W. Kook, Categories of acyclic graphs and automorphisms of free groups, Ph.D. thesis (G. Carlsson, advisor), Stanford University, 1996
-
for n from 1 to 50 do printf(`%d,`, (n-1)*sum((n-2)!/(2^k*k!*(n-2-2*k)!)*n^(n-2-2*k), k=0..floor((n-2)/2))) od:
-
s=20;(*generates first s terms starting from n=2*) K := Exp[Sum[(m-1)*(m^(m-2))*(x^m)/m!, {m, 2, 2s}]]; S := Series[K, {x, 0, s}]; h[i_] := SeriesCoefficient[S, i-1]*(i-1)!; Table[h[n+1], {n, s}]
a[n_] := (n-2)*Sum[ (n-1)^(n-2k-3)*(n-3)! / (2^k*k!*(n-2k-3)!), {k, 0, Floor[ (n-3)/ 2 ]}]; a[1] = 1; Table[a[n], {n, 1, 19}] (* Jean-François Alcover, Dec 11 2012, after Maple *)
-
a(n)=if(n<1,0,(n-1)!*polcoeff(exp(sum(k=1,n-1,k^(k-1)*x^k/k!,O(x^n))^2/2),n-1))
-
a(n)=if(n<2,n==1,sum(k=0,(n-3)\2,(n-1)!/(2^k*k!*(n-3-2*k)!)*(n-1)^(n-4-2*k)))
-
df(n)=(2*n)!/(n!*2^n); \\ A001147
he(n,x)=x^n+sum(k=1, n\2, binomial(n,2*k) * df(k) * x^(n-2*k) );
a(n)=if( n<3, n==1, (n-2)*he(n-3, n-1) );
/* Joerg Arndt, May 06 2013 */
Additional comments from Woong Kook (andrewk(AT)math.uri.edu), Feb 12 2002
Updated author's URL and e-mail address
R. J. Mathar, May 23 2010
A060917
Expansion of e.g.f.: exp((-1)^k/k*LambertW(-x)^k)/(k-1)!, k=3.
Original entry on oeis.org
1, 12, 150, 2180, 36855, 715008, 15697948, 385300800, 10463945085, 311697869120, 10108450408914, 354630018043392, 13384651003544275, 540860323696035840, 23300648262667635960, 1066165291831917811712
Offset: 3
-
nn = 20; CoefficientList[Series[E^(-1/3*LambertW[-x]^3)/2, {x, 0, nn}], x]* Range[0, nn]! (* Vaclav Kotesovec, Nov 27 2012 *)
-
x='x+O('x^30); Vec(serlaplace(exp(-lambertw(-x)^3/3)/2 - 1/2)) \\ G. C. Greubel, Feb 19 2018
Showing 1-3 of 3 results.
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