OFFSET
1,18
FORMULA
a(n) = Sum_{i=1..floor(n/2)} (1 - mu(i)^2) * mu(n-i)^2, where mu is the Möbius function (A008683).
MATHEMATICA
Table[Sum[(1 - MoebiusMu[k]^2) (MoebiusMu[n - k]^2), {k, Floor[n/2]}], {n, 80}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Oct 25 2017
STATUS
approved