OFFSET
1,3
FORMULA
a(n) = Sum_{i=1..floor((n-1)/2)} i * (n-i) * (floor((n-i)/i) - floor((n-i-1)/i)).
MATHEMATICA
Table[Sum[i (n - i) (Floor[(n - i)/i] - Floor[(n - i - 1)/i]), {i, Floor[(n - 1)/2]}], {n, 80}]
PROG
(Magma) [0, 0] cat [&+[k*(n-k)*(((n-k) div k)-((n-k-1) div k)): k in [1..(n-1) div 2]]: n in [3..80]]; // Vincenzo Librandi, Apr 23 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wesley Ivan Hurt, Apr 22 2018
STATUS
approved