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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.
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%I #5 Feb 05 2014 20:18:18

%S 1,2,6,9,56,23,399,442,2220,2386,71577,22001,1179483,1156519,4975079

%N 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 Sequence suggested by _Leroy Quet_ on the SeqFan mailing list.

%e 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 Cf. A076220, A117542.

%K nonn

%O 1,2

%A _Giovanni Resta_, Mar 28 2006