OFFSET
1,1
COMMENTS
This is obviously the same as rankings of (even i, odd j) when ordered according to i+j/r, since the position of the pair in the original list does not matter. [Observation of Charles R Greathouse IV, Feb 13 2011.]
EXAMPLE
Writing (i,j) for i+r*j, the first 7 in the ranking are
(0,0), (1,0), (0,1), (2,0), (1,1), (3,0), (0,2);
the ranks where i is odd and j is even are a(1)=2 and a(2)=6. If sorted according to the value of i+j/r, the list is the same with i,j exchanged.
CROSSREFS
KEYWORD
nonn
AUTHOR
Clark Kimberling, Jan 08 2011
STATUS
approved