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Number of up-down sequences with n copies each of 1,2,...,5.
1

%I #4 Sep 08 2016 08:32:09

%S 1,16,936,87336,9929000,1267945800,174470351760,25288627665840,

%T 3812023555600680,591698219294831040,94094630284245419136,

%U 15245574601442117896656,2511237778001138580615056,419023242828557373939828896,70761397145460782667032755200

%N Number of up-down sequences with n copies each of 1,2,...,5.

%e a(1) = 16: 13254, 14253, 14352, 15243, 15342, 23154, 24153, 24351, 25143, 25341, 34152, 34251, 35142, 35241, 45132, 45231.

%e a(2) = 936: 1213243545, 1213254534, 1214243535, 1214253435, ..., 4545121323, 4545132312, 4545231213, 4545231312.

%Y Row n=5 of A275784.

%K nonn

%O 0,2

%A _Alois P. Heinz_, Sep 08 2016