STATUS
reviewed
approved
The OEIS is supported by the many generous donors to the OEIS Foundation.
Revision History for A218321
(Bold, blue-underlined text is an addition; faded, red-underlined text is aShowing entries 1-10 | older changes
Number of lattice paths from (0,0) to (n,n) which do not go above the diagonal x=y using steps (1,k), (k,1) with k>=0.
(history; published version)
(history; published version)
STATUS
proposed
reviewed
STATUS
editing
proposed
MATHEMATICA
b[x_, y_] := b[x, y] = If[y < 0 || y > x, 0, If[x == 0, 1, Sum[b[x - i, y - 1], {i, 0, x}] + Sum[b[x - 1, y - j], {j, 0, y}] - b[x - 1, y - 1]]];
a[n_] := b[n, n];
Table[a[n], {n, 0, 30}] (* Jean-François Alcover, Sep 01 2022, after Alois P. Heinz *)
STATUS
approved
editing
STATUS
editing
approved
STATUS
editing
approved
STATUS
editing
approved
CROSSREFS
Cf. A082582.
STATUS
approved
editing