%I A099743
%S A099743 0,0,2,15,75,313,1179,4161,14051,45993,147195,463345,1440723,4438905,
%T A099743 13582955,41350977,125404611,379228489,1144370139,3447856017,
%U A099743 10375942835,31198607385,93749962827,281584384225,845476670115
%N A099743 Number of permutations with exactly 1 valley which avoid the pattern 
               1324.
%F A099743 G.f.: (2-3*x)*x^3/((1-2*x)^3*(1-3*x)).
%e A099743 a(3)=2 because 213 and 312 have exactly 1 valley and avoid 1324
%Y A099743 Cf. A000079.
%Y A099743 Sequence in context: A056037 A125903 A007232 this_sequence A102289 A041243 
               A056079
%Y A099743 Adjacent sequences: A099740 A099741 A099742 this_sequence A099744 A099745 
               A099746
%K A099743 nonn
%O A099743 1,3
%A A099743 Mike Zabrocki (zabrocki(AT)mathstat.yorku.ca), Nov 09 2004