Search: id:A093346
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%I A093346
%S A093346 1,1,2,1,3,6,1,4,15,22,1,5,28,95,91,1,6,45,252,690,408,1,7,66,525,2618,
%T A093346 5481,1938,1,8,91,946,7095,29848,46376,9614,1,9,120,1547,15741,105417,
%U A093346 363216,411255,49335,1,10,153,2360,30576,288288,1673535
%N A093346 Array read by antidiagonals: T(r,n) = number of two-stack sortable r-permutations.
%H A093346 D. Xu, <a href="http://arXiv.org/abs/math.CO/0209313">Generalizations 
               of two-stack-sortable permutations</a>, PhD thesis.
%F A093346 T(r, n) = 2(r+1) * ((2r+1)n)!/[n!*(2rn+2)! ]
%o A093346 (PARI) T(r,n)=2*(r+1)*((2*r+1)*n)!/(n!*(2*r*n+2)!)
%Y A093346 Sequence in context: A046899 A035206 A115196 this_sequence A115597 A103371 
               A120257
%Y A093346 Adjacent sequences: A093343 A093344 A093345 this_sequence A093347 A093348 
               A093349
%K A093346 nonn,tabl
%O A093346 1,3
%A A093346 Ralf Stephan, Apr 26 2004

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