OFFSET
1,2
COMMENTS
See A187645.
FORMULA
a(n) = n + floor(((1/4)*n^3 - 1/8)^(1/2)).
EXAMPLE
Write preliminary separate rankings:
1/4...2....27/4....16.....125/4...
....1...4.......9..16..25........36..49
Then replace each number by its rank, where ties are settled by ranking the top number before the bottom.
MATHEMATICA
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Clark Kimberling, Feb 13 2011
STATUS
approved