%I A117542
%S A117542 1,2,6,8,36,16,127,320,581,1564,13565,13760,149186,773727,540538
%N A117542 Number of permutations P of 1..n such that in P and in the inverse of 
               P, every pair of adjacent numbers and the first and last number, 
               are relatively prime.
%C A117542 Sequence suggested by Leroy Quet on the SeqFan mailing list.
%H A117542 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A117542 a(4)=8, since the 8 permutations (1,2,3,4), (1,4,3,2), (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 A117542 Cf. A076220, A117541.
%Y A117542 Sequence in context: A019199 A094678 A076507 this_sequence A045653 A152158 
               A095239
%Y A117542 Adjacent sequences: A117539 A117540 A117541 this_sequence A117543 A117544 
               A117545
%K A117542 nonn
%O A117542 1,2
%A A117542 Giovanni Resta (g.resta(AT)iit.cnr.it), Mar 28 2006