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

Terms

a(0) =2a(1) =4a(2) =17a(3) =20a(4) =57a(5) =67a(6) =121a(7) =116a(8) =224a(9) =239a(10) =343a(11) =371a(12) =535a(13) =487a(14) =777a(15) =660a(16) =1005a(17) =958a(18) =1275a(19) =1095a(20) =1669a(21) =1401a(22) =1911a(23) =1715a(24) =2482a(25) =2097a(26) =3005a(27) =2295a(28) =3163a(29) =2987