OFFSET
1,2
COMMENTS
If p is prime, a(p) = Sum_{d|p} d * mu(d) * floor(p/d^2) = 1*1*p + p*(-1)*0 = p.
EXAMPLE
a(10) = Sum_{d|10} d * mu(d) * floor(10/d^2) = 1*1*10 + 2*(-1)*2 + 5*(-1)*0 + 10*1*0 = 6.
MATHEMATICA
Table[Sum[k*MoebiusMu[k] Floor[n/k^2] (1 - Ceiling[n/k] + Floor[n/k]), {k, n}], {n, 80}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Wesley Ivan Hurt, May 18 2021
STATUS
approved