%I A117541
%S A117541 1,2,6,9,56,23,399,442,2220,2386,71577,22001,1179483,1156519,4975079
%N A117541 Number of permutations P of 1..n such that in P and in the inverse of 
               P, every pair of adjacent numbers are relatively prime.
%C A117541 Sequence suggested by Leroy Quet on the SeqFan mailing list.
%H A117541 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A117541 a(4)=9, since the 9 permutations (1,2,3,4), (1,4,3,2), (2,1,3,4), (2,
               1,4,3), (2,3,4,1), (4,1,2,3), (3,2,1,4), (3,4,1,2), (4,3,2,1) satisfy 
               the property.
%Y A117541 Cf. A076220, A117542.
%Y A117541 Sequence in context: A082459 A129831 A101713 this_sequence A095105 A052194 
               A073662
%Y A117541 Adjacent sequences: A117538 A117539 A117540 this_sequence A117542 A117543 
               A117544
%K A117541 nonn
%O A117541 1,2
%A A117541 Giovanni Resta (g.resta(AT)iit.cnr.it), Mar 28 2006