OFFSET
0,4
COMMENTS
More generally if r is irrational 1<r<2 then sum(k=1,n,floor(r*floor(k/r))) = n(n-3)/2 + ceiling(n/r)
FORMULA
a(n) = n(n-3)/2 + ceiling(n/sqrt(3))
CROSSREFS
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Jun 15 2003
STATUS
approved