A063179 Di-Boustrophedon transform of (1,0,0,0,...): Fill in an array by diagonals alternating in the 'up' and 'down' directions. The n-th diagonal starts with the n-th element of (1,0,0,0,...). When going in the 'up' direction the next element is the sum of the previous element of the diagonal and the previous two elements of the row the new element is in. When going in the 'down' direction the next element is the sum of the previous element of the diagonal and the previous two elements of the column the new element is in. The final element of the n-th diagonal is a(n).

1, 1, 2, 4, 12, 42, 178, 870, 4830, 29976, 205572, 1543210, 12583242, 110725638, 1045664646, 10547679660, 113172039256, 1286925785286, 15459448549274, 195616259182162, 2600506074185090, 36235386548738016, 528084808585261568, 8033872923106040478

Offset

1,3

Links

Table of n, a(n) for n=1..24.

Example

Array begins:
   1  1  0  4  0 42 ...
   0  1  3  4 38 ...
   2  2  7 31 ...
   0 10 22 ...
  12 12 ...
   0 ...

Crossrefs

Cf. A000667, A059216, A062704, A063180, A063181.

Sequence in context: A188494 A202668 A200222 * A096802 A139669 A179973

Adjacent sequences: A063176 A063177 A063178 * A063180 A063181 A063182

Keyword

easy,nonn

Author

Floor van Lamoen, Jul 09 2001

Extensions

More terms from Sean A. Irvine, Apr 21 2023

Status

approved