OFFSET
1,5
FORMULA
a(n) = Sum_{k=1..n} k * c(k) * (ceiling(n/k) - floor(n/k)), where c = A010052.
EXAMPLE
a(17) = 29 since the sum of the squares less than 17 that do not divide 17 is 4 + 9 + 16 = 29.
MATHEMATICA
Table[Sum[k*(Floor[Sqrt[k]] - Floor[Sqrt[k - 1]]) (Ceiling[n/k] - Floor[n/k]), {k, n}], {n, 100}]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Jan 06 2024
STATUS
approved