OFFSET
1,2
FORMULA
a(n) = n * Sum_{i=1..floor(n/2)} i * mu(i)^2 * mu(n-i)^2, where mu is the Möbius function (A008683).
a(n) = n * A261985(n). - Wesley Ivan Hurt, Jan 05 2024
MATHEMATICA
Table[n*Sum[i*MoebiusMu[i]^2 MoebiusMu[n - i]^2, {i, Floor[n/2]}], {n, 80}]
PROG
(Magma) [0] cat [&+[n*k*MoebiusMu(k)^2*MoebiusMu(n-k)^2: k in [1..Floor(n/2)]]: n in [2..60]]; // Vincenzo Librandi, Apr 21 2018
(PARI) a(n) = n * sum(i=1, n\2, i * moebius(i)^2 * moebius(n-i)^2); \\ Michel Marcus, Apr 21 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 19 2018
STATUS
approved