OFFSET
1,4
FORMULA
a(n) = Sum_{i=1..floor(n/2)} i * mu(n-i)^2, where mu is the Möbius function (A008683).
MATHEMATICA
Table[Sum[i*MoebiusMu[n - i]^2, {i, Floor[n/2]}], {n, 80}]
Table[Total[Select[IntegerPartitions[n, {2}], SquareFreeQ[#[[1]]]&][[All, 2]]], {n, 70}] (* Harvey P. Dale, Dec 26 2020 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Oct 23 2017
STATUS
approved