OFFSET
1,3
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
EXAMPLE
a(5)=mu(1)*sigma(4)+mu(2)*sigma(3)+mu(3)*sigma(2)+mu(4)*sigma(1)
= 1*7 - 1*4 - 1*3 + 0*1 = 0.
PROG
(PARI) a(n)=sum(i=1, n-1, moebius(i)*sigma(n-i)) \\ Charles R Greathouse IV, Feb 14 2013
CROSSREFS
KEYWORD
sign
AUTHOR
Reinhard Zumkeller, Oct 07 2005
STATUS
approved