OFFSET
0,4
FORMULA
From Franklin T. Adams-Watters, Feb 06 2006: (Start)
G.f.: (x+y-3xy+x^2 y^2)/((1-x)^2 (1-y)^2 (1-xy)).
a(n) = (1/2)*(t - 1 + abs(t^2 - 2*n - 1)), where t = floor(sqrt(2*n+1)+1/2). - Ridouane Oudra, May 03 2019
EXAMPLE
Top left corner of array:
0 1 2 3
1 1 2 3
2 2 2 3
3 3 3 3
CROSSREFS
KEYWORD
tabl,nonn
AUTHOR
STATUS
approved