Search: id:A107761
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%I A107761
%S A107761 1,2,6,24,72,480,3600,9600,108000,1270080,4795200,74088000,768539520,
%T A107761 4759413120,94182359040,1893397524480,11353661706240,122634632171520,
%U A107761 3104438623534080,23063946114908160,664424069072117760
%N A107761 Number of permutations of (1,3,5,7,9,...,2n-1) where every adjacent pair 
               in the permutation are coprime.
%C A107761 Odd analogue of A076220.
%D A107761 a(1)-a(9) computed by Zak Seidov.
%H A107761 Leroy Quet, <a href="http://www.prism-of-spirals.net/">Home Page</a> 
               (listed in lieu of email address)
%e A107761 For example, if n = 5, the permutation (5,3,7,9,1) is counted, but (5,
               3,9,1,7) is not counted because 3 and 9 are adjacent.
%t A107761 With[{n=9}, per=Permutations[Range[1, 2 n -1, 2]]; Select[per, Times 
               @@ Table[GCD @@Partition[ #, 2, 1][[i]], {i, n-1}]==1&]//Length] 
               (Seidov)
%Y A107761 Cf. A076220, A086595, A102381, A107762, A107763.
%Y A107761 Sequence in context: A027562 A096259 A087645 this_sequence A147943 A147934 
               A147925
%Y A107761 Adjacent sequences: A107758 A107759 A107760 this_sequence A107762 A107763 
               A107764
%K A107761 nonn
%O A107761 1,2
%A A107761 Ray Chandler (rayjchandler(AT)sbcglobal.net), following a suggestion 
               of Leroy Quet, Jun 11 2005
%E A107761 More terms from Max Alekseyev (maxale(AT)gmail.com), Jun 11 2005

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