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Triangle read by rows, arising in the enumeration of corners.
1

%I #14 Nov 07 2017 18:28:11

%S 1,0,1,0,2,1,0,3,2,1,0,4,5,2,1,0,5,8,5,2,1,0,6,14,10,5,2,1,0,7,20,18,

%T 10,5,2,1,0,8,30,30,20,10,5,2,1

%N Triangle read by rows, arising in the enumeration of corners.

%H G. Kreweras, <a href="http://dx.doi.org/10.1016/0012-365X(79)90163-8">Sur les extensions linéaires d'une famille particuliere d'ordres partiels</a>, Discrete Math., 27 (1979), 279-295.

%H G. Kreweras, <a href="/A006330/a006330_1.pdf">Sur les extensions linéaires d'une famille particulière d'ordres partiels</a>, Discrete Math., 27 (1979), 279-295. (Annotated scanned copy)

%F Kreweras gives a recurrence on page 281.

%e Triangle begins:

%e 1;

%e 0, 1;

%e 0, 2, 1;

%e 0, 3, 2, 1;

%e 0, 4, 5, 2, 1;

%e 0, 5, 8, 5, 2, 1;

%e 0, 6, 14, 10, 5, 2, 1;

%e 0, 7, 20, 18, 10, 5, 2, 1;

%e 0, 8, 30, 30, 20, 10, 5, 2, 1;

%e ...

%Y Row sums = A006330.

%K nonn,tabl,more

%O 0,5

%A _N. J. A. Sloane_, Jun 22 2015