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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). 2
1, 2, 6, 22, 105, 631, 4603, 39469, 388870, 4327322, 53670985, 734069672, 10975379510, 178080287645, 3116286236549, 58502460526469 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..15.

Index entries for sequences related to boustrophedon transform

CROSSREFS

Cf. A064641. Table: A064644, Delannoy numbers A008288.

Sequence in context: A129815 A251181 A103941 * A218531 A129535 A216720

Adjacent sequences:  A064640 A064641 A064642 * A064644 A064645 A064646

KEYWORD

nonn

AUTHOR

Floor van Lamoen, Oct 03 2001

STATUS

approved

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Last modified February 20 10:45 EST 2018. Contains 299385 sequences. (Running on oeis4.)