a(n) = n^2 * Sum_{d|n} (-1)^(n/d + 1) * mu(d) / d^2.

Terms

a(0) =1a(1) =-5a(2) =8a(3) =-12a(4) =24a(5) =-40a(6) =48a(7) =-48a(8) =72a(9) =-120a(10) =120a(11) =-96a(12) =168a(13) =-240a(14) =192a(15) =-192a(16) =288a(17) =-360a(18) =360a(19) =-288a(20) =384a(21) =-600a(22) =528a(23) =-384a(24) =600a(25) =-840a(26) =648a(27) =-576a(28) =840a(29) =-960