%I #12 Oct 17 2017 14:31:41
%S 1,4,28,258,2892,37778,560124,9256010,168182044,3325057826,
%T 70934634236,1621828212826,39517131361884,1021237022557682,
%U 27877344103738940,800976143703407210,24148078430008534428
%N E.g.f. exp(sum_{d|M} (exp(d*x)-1)/d), M=6.
%H Vincenzo Librandi, <a href="/A141004/b141004.txt">Table of n, a(n) for n = 0..200</a>
%t u[0,j_]:=1;u[k_,j_]:=u[k,j]=Sum[Binomial[k-1,i-1]Plus@@(u[k-i,j]#^(i-1)&/@Divisors[j]),{i,k}]; Table[u[n,6],{n,0,12}] [From _Wouter Meeussen_, Dec 06 2008]
%Y u[n,j] generates for j=1, A000110 Bell numbers; j=2, A002872 "Sorting numbers"; j=3, A002874 "Sorting numbers"; j=4, A141003 (Mathar); j=5, A036075 "Sorting numbers"; j=6, A141004 (Mathar); j=7, A036077 "Sorting numbers" [From _Wouter Meeussen_, Dec 06 2008]
%Y Column k=6 of A162663.
%K nonn
%O 0,2
%A _R. J. Mathar_, Jul 11 2008