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A180836 Number of nX2 arrays containing 2 indistinguishable copies of 1..n with rows and columns in lexicographically strictly increasing order 0

%I

%S 1,1,9,72,678,7719,102963,1573764,27143466,521698683,11059018599,

%T 256349691978,6451098232944

%N Number of nX2 arrays containing 2 indistinguishable copies of 1..n with rows and columns in lexicographically strictly increasing order

%C Column 2 of A180839

%e Some solutions for 4X2

%e ..1..1....1..1....1..1....1..1....1..1....1..1....1..1....1..1....1..1....1..3

%e ..2..3....2..3....2..3....2..3....2..3....2..2....2..4....2..4....2..4....1..4

%e ..3..2....3..4....2..4....2..4....4..2....3..4....3..3....3..2....3..2....3..2

%e ..4..4....4..2....4..3....3..4....4..3....4..3....4..2....4..3....3..4....4..2

%e ...

%e ..1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..3

%e ..1..4....1..4....1..4....1..4....1..4....3..2....2..1....2..1....2..1....2..1

%e ..2..3....2..3....2..2....2..2....2..4....4..1....3..2....3..4....2..3....2..4

%e ..4..2....2..4....4..3....3..4....3..2....4..2....4..4....4..2....4..4....4..3

%e ...

%e ..1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..3....1..2

%e ..2..1....2..1....2..3....2..3....2..2....2..2....2..2....2..4....2..4....1..3

%e ..2..4....4..2....2..4....4..1....3..1....3..4....4..1....3..1....3..2....3..2

%e ..3..4....4..3....4..1....4..2....4..4....4..1....4..3....4..2....4..1....4..4

%K nonn

%O 1,3

%A _R. H. Hardin_ Sep 20 2010

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Last modified June 25 17:46 EDT 2022. Contains 354851 sequences. (Running on oeis4.)