a(n) = lcm(n, phi(n), n - phi(n)).

Terms

a(0) =0a(1) =2a(2) =6a(3) =4a(4) =20a(5) =12a(6) =42a(7) =8a(8) =18a(9) =60a(10) =110a(11) =24a(12) =156a(13) =168a(14) =840a(15) =16a(16) =272a(17) =36a(18) =342a(19) =120a(20) =252a(21) =660a(22) =506a(23) =48a(24) =100a(25) =1092a(26) =54a(27) =336a(28) =812a(29) =1320