%I A109034
%S A109034 1,0,1,4,16,66,280,1216,5384,24224,110464,509480,2372704,11142656,
%T A109034 52709600,250933120,1201354240,5780413760,27937867520,135574988800,
%U A109034 660314620160,3226731934720,15815752724480,77735943378560
%N A109034 First differences of A109033.
%D A109034 Ian Le, Wilf classes of pairs of permutations of length 4, The Electronic 
               J. of Combinatorics, 12, 2005, R25.
%F A109034 G.f.=[1-sqrt(1-8x+16x^2-8x^3)]/[4x]
%p A109034 G:=(1-sqrt(1-8*x+16*x^2-8*x^3))/4/x: Gser:=series(G,x=0,30): 1,seq(coeff(Gser,
               x^n),n=1..27);
%Y A109034 Cf. A109033.
%Y A109034 Sequence in context: A026762 A082307 A099782 this_sequence A110276 A026883 
               A151242
%Y A109034 Adjacent sequences: A109031 A109032 A109033 this_sequence A109035 A109036 
               A109037
%K A109034 nonn
%O A109034 0,4
%A A109034 Emeric Deutsch (deutsch(AT)duke.poly.edu), Jun 16 2005