a(n) = n^2 * Sum_{primes p dividing n} (1 - 1/p^2).

Terms

a(0) =0a(1) =3a(2) =8a(3) =12a(4) =24a(5) =59a(6) =48a(7) =48a(8) =72a(9) =171a(10) =120a(11) =236a(12) =168a(13) =339a(14) =416a(15) =192a(16) =288a(17) =531a(18) =360a(19) =684a(20) =824a(21) =843a(22) =528a(23) =944a(24) =600a(25) =1179a(26) =648a(27) =1356a(28) =840a(29) =2339