OFFSET
1,5
FORMULA
a(n) = Sum_{i=1..floor((n-1)/2} mu(i*(n-2*i))^2, where mu is the Möbius function (A008683).
MATHEMATICA
Table[Sum[MoebiusMu[i (n - 2 i)]^2, {i, Floor[(n - 1)/2]}], {n, 100}]
PROG
(Magma) [0, 0] cat [&+[MoebiusMu(k*(n-2*k))^2: k in [1..((n-1) div 2)]]: n in [3..80]]; // Vincenzo Librandi, Apr 21 2018
(PARI) a(n) = sum(i=1, (n-1)\2, moebius(i*(n-2*i))^2); \\ Michel Marcus, Apr 21 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 19 2018
STATUS
approved