A076543 Sum(k=1 to n) k*sqf(k); sqf(k)=1 if k is squarefree and sqf(k)=-1 otherwise.

1, 3, 6, 2, 7, 13, 20, 12, 3, 13, 24, 12, 25, 39, 54, 38, 55, 37, 56, 36, 57, 79, 102, 78, 53, 79, 52, 24, 53, 83, 114, 82, 115, 149, 184, 148, 185, 223, 262, 222, 263, 305, 348, 304, 259, 305, 352, 304, 255, 205, 256, 204, 257, 203, 258, 202, 259, 317, 376, 316, 377