%I A060963
%S A060963 1,1,5,29,145,957,8397,85169,944221,11639417,160699437,2430145085,
%T A060963 39776366397
%N A060963 Number of pairings of the first 2n integers so that the differences of 
               each pair are different.
%C A060963 Number of perfect Skolem-type sequences.
%H A060963 G. Nordh, <a href="http://arXiv.org/abs/math.NT/0506155">Perfect Skolem 
               sequences</a>
%e A060963 a(3)=5 since the 5 pairings of {1, 2, 3, 4, 5, 6} are: {1, 3} {2, 6} 
               {4, 5}, {1, 5} {2, 3} {4, 6}, {1, 5} {2, 4} {3, 6}, {1, 4} {2, 6} 
               {3, 5}, {1, 6} {2, 5} {3, 4}
%Y A060963 Sequence in context: A034332 A146053 A163082 this_sequence A107002 A027864 
               A065541
%Y A060963 Adjacent sequences: A060960 A060961 A060962 this_sequence A060964 A060965 
               A060966
%K A060963 nonn
%O A060963 0,3
%A A060963 Erich Friedman (efriedma(AT)stetson.edu), May 08 2001