%I A054873
%S A054873 1,2,6,24,120,720,5040,40320,357840,3427200,34685280,365541120,
%T A054873 3971615760,44181889920,500788985760,5763231048960,67163932069920,
%U A054873 791030794095360,9400660122813120,112587818898562560
%N A054873 Number of (S_5 67)-avoiding permutations.
%D A054873 E. Barcucci, A. Del Lungo, E. Pergola, R. Pinzani, Permutations avoiding 
               an increasing number of length-increasing forbidden subsequences, 
               Discrete MAthematics and Theoretical Computer Science 4, 2000, 31-44
%H A054873 E. Barcucci, A. Del Lungo, E. Pergola and R. Pinzani, <a href="http:/
               /www.dmtcs.org/volumes/abstracts/dm040103.abs.html">Permutations 
               avoiding an increasing number of length-increasing forbidden subsequences</
               a>
%F A054873 f := (x, j)->1-(j+1)*x- sqrt(1-2*(j+1)*x+(j-1)^2*x^2); t := (x, j)->sum(k!*x^k, 
               k=1..(j-1)); s := (x, j)->x^(j-2)*(j-1)!*(f(x, j))/(2)+ t(x, j); 
               j := 6
%Y A054873 Cf. A000108.
%Y A054873 Sequence in context: A152644 A152637 A152645 this_sequence A072132 A066459 
               A071937
%Y A054873 Adjacent sequences: A054870 A054871 A054872 this_sequence A054874 A054875 
               A054876
%K A054873 nonn
%O A054873 1,2
%A A054873 Elisa Pergola (elisa(AT)dsi.unifi.it), May 26 2000