OFFSET
1,6
LINKS
B. D. Swan, Table of n, a(n) for n=1..10000
FORMULA
a(n) = Sum_{i=1..n} (i-1)*floor((n-i)/i). - Wesley Ivan Hurt, Sep 13 2017
MATHEMATICA
Accumulate[Array[DivisorSigma[1, #]-DivisorSigma[0, #]-#+1&, 70]] (* Harvey P. Dale, Dec 27 2011 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Omar E. Pol, Dec 22 2008
STATUS
approved