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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(n-1,k-1) + T(n-1,k) + T(n-2,k-1), 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).

%I A064643 #6 Mar 02 2015 16:08:47
%S A064643 1,2,6,22,105,631,4603,39469,388870,4327322,53670985,734069672,
%T A064643 10975379510,178080287645,3116286236549,58502460526469
%N 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(n-1,k-1) + T(n-1,k) + T(n-2,k-1), 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).
%H A064643 <a href="/index/Bo#boustrophedon">Index entries for sequences related to boustrophedon transform</a>
%Y A064643 Cf. A064641. Table: A064644, Delannoy numbers A008288.
%K A064643 nonn
%O A064643 0,2
%A A064643 _Floor van Lamoen_, Oct 03 2001