OFFSET
1,5
MAPLE
MATHEMATICA
nmax = 12; a[_, 1] = 1; a[1, _] = 1; a[n_ /; n > 1, k_ /; k > 1] := a[n, k] = 1 + a[n-1, k-1] + a[n-1, k] + a[n, k-1]; Flatten[ Table[ a[n-k , k], {n, 1, nmax}, {k, 1, n-1}]] (* Jean-François Alcover, Jul 19 2012 *)
CROSSREFS
KEYWORD
AUTHOR
EXTENSIONS
Description corrected by Henry Bottomley, May 09 2000
STATUS
approved