OFFSET
0,2
FORMULA
a(n-1)=sum_{k=1...n}mu(k)floor(n/k)ceiling(n/k); a(n) is asymptotic to (6/Pi^2)*n^2 - Benoit Cloitre, Jun 27 2005
PROG
(PARI) a(n)=sum(k=1, n++, n\k*moebius(k)*ceil(n/k)) \\ Charles R Greathouse IV, Mar 02 2012
CROSSREFS
KEYWORD
nonn
AUTHOR
STATUS
approved