OFFSET
1,3
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..3000
FORMULA
a(n) = Sum_{i=1..n} mu(n*i)^2, where mu is the Moebius function (A008683). - Ridouane Oudra, Jul 24 2019
MAPLE
seq(add(mobius(n*i)^2, i = 1 .. n), n = 1 .. 90); # Ridouane Oudra, Jul 24 2019
MATHEMATICA
Count[#, _?SquareFreeQ]&/@Table[k*n, {n, 90}, {k, n}] (* Harvey P. Dale, Sep 05 2012 *)
Table[Sum[MoebiusMu[i n]^2, {i, n}], {n, 100}] (* Vincenzo Librandi, Jul 25 2019 *)
PROG
(Magma) [&+[MoebiusMu(k*n)^2: k in [1..n]]: n in [1..80]]; // Vincenzo Librandi, Jul 25 2019
CROSSREFS
KEYWORD
nonn
AUTHOR
Reinhard Zumkeller, Apr 05 2010
STATUS
approved