

A064643


Bidirectional 'Delannoy' variation of the Boustrophedon transform applied to all 1's sequence: Fill an triangular array in alternating directions. Let the first element of each row in that direction be equal to 1. Each next entry is given by T(n,k) = T(n,k +/ 1) + T(n1,k1) + T(n1,k) + T(n2,k1), where the +/ depends on which is the previous element in the direction one is filling in the row. The final number of row n gives a(n).


2



1, 2, 6, 22, 105, 631, 4603, 39469, 388870, 4327322, 53670985, 734069672, 10975379510, 178080287645, 3116286236549, 58502460526469
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