OFFSET
1,2
FORMULA
MATHEMATICA
Table[Sum[MoebiusMu[k] Ceiling[n/k]^2, {k, 1, n}], {n, 1, 54}]
Join[{1}, Table[2 + Sum[2 EulerPhi[k - 1] + MoebiusMu[k], {k, 2, n}], {n, 2, 54}]]
PROG
(PARI) a(n) = sum(k=1, n, moebius(k)*ceil(n/k)^2); \\ Michel Marcus, Feb 21 2020
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Feb 19 2020
STATUS
approved