cp's OEIS Frontend

A218868 Triangular array read by rows: T(n,k) is the number of n-permutations that have exactly k distinct cycle lengths.

%I A218868 #28 Jul 26 2018 16:59:33
%S A218868 1,2,3,3,10,14,25,95,176,424,120,721,3269,1050,6406,21202,12712,42561,
%T A218868 178443,141876,436402,1622798,1418400,151200,3628801,17064179,
%U A218868 17061660,2162160,48073796,177093256,212254548,41580000,479001601,2293658861,2735287698,719072640
%N A218868 Triangular array read by rows: T(n,k) is the number of n-permutations that have exactly k distinct cycle lengths.
%C A218868 T(A000217(n),n) gives A246292. - _Alois P. Heinz_, Aug 21 2014
%H A218868 Alois P. Heinz, <a href="/A218868/b218868.txt">Rows n = 1..170, flattened</a>
%H A218868 P. Flajolet and R. Sedgewick, <a href="http://algo.inria.fr/flajolet/Publications/AnaCombi/anacombi.html">Analytic Combinatorics</a>, Cambridge University Press, 2009
%F A218868 E.g.f.: Product_{i>=1} (1 + y*exp(x^i/i) - y).
%e A218868 :      1;
%e A218868 :      2;
%e A218868 :      3,       3;
%e A218868 :     10,      14;
%e A218868 :     25,      95;
%e A218868 :    176,     424,     120;
%e A218868 :    721,    3269,    1050;
%e A218868 :   6406,   21202,   12712;
%e A218868 :  42561,  178443,  141876;
%e A218868 : 436402, 1622798, 1418400, 151200;
%p A218868 with(combinat):
%p A218868 b:= proc(n, i) option remember; expand(`if`(n=0, 1,
%p A218868       `if`(i<1, 0, add((i-1)!^j*multinomial(n, n-i*j, i$j)/j!*
%p A218868       b(n-i*j, i-1)*`if`(j=0, 1, x), j=0..n/i))))
%p A218868     end:
%p A218868 T:= n-> (p-> seq(coeff(p, x, i), i=1..degree(p)))(b(n$2)):
%p A218868 seq(T(n), n=1..16);  # _Alois P. Heinz_, Aug 21 2014
%t A218868 nn=10;a=Product[1-y+y Exp[x^i/i],{i,1,nn}];f[list_]:=Select[list,#>0&];Map[f,Drop[Range[0,nn]!CoefficientList[Series[a ,{x,0,nn}],{x,y}],1]]//Grid
%Y A218868 Columns k=1-3 give: A005225, A005772, A133119.
%Y A218868 Row sums are: A000142.
%Y A218868 Row lengths are: A003056.
%Y A218868 Cf. A208437, A242027 (the same for endofunctions), A246292, A317327.
%K A218868 nonn,tabf
%O A218868 1,2
%A A218868 _Geoffrey Critzer_, Nov 07 2012