%I A006989
%S A006989 1,0,2,4,34,196,1826,17172,199074,2510116,35862562,559572916,
%T A006989 9577862306,177417693636,3546104002338,75961485384532,1737273637523362,
%U A006989 42235881659123812,1087865420946370082,29589907884231535860
%N A006989 Log of g.f. of numbers of preferential arrangements.
%C A006989 If A= e.g.f. for A006989 and B = e.g.f. for A000670, then A = log(1+\int(B))'.
%o A006989 (PARI) a(n)=if(n<0,0,n!*polcoeff(log(1+intformal(1/(2-exp(x+x*O(x^n)))))',
               n))
%Y A006989 Cf. A000670.
%Y A006989 Sequence in context: A099433 A051225 A103625 this_sequence A132529 A140984 
               A057996
%Y A006989 Adjacent sequences: A006986 A006987 A006988 this_sequence A006990 A006991 
               A006992
%K A006989 nonn
%O A006989 0,3
%A A006989 N. J. A. Sloane (njas(AT)research.att.com).