OFFSET
1,2
EXAMPLE
Writing (i,j) for i+j*r, the first 7 in the ranking are (0,0), (1,0), (0,1), (2,0), (1,1), (0,2), (3,0); the ranks where i and j are both even are 1,4,6.
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 12 2011
STATUS
approved