LCM of numbers <= n and having a factor in common with n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =12a(6) =7a(7) =24a(8) =18a(9) =120a(10) =11a(11) =360a(12) =13a(13) =840a(14) =180a(15) =1680a(16) =17a(17) =5040a(18) =19a(19) =5040a(20) =1260a(21) =55440a(22) =23a(23) =55440a(24) =300a(25) =720720a(26) =7560a(27) =720720a(28) =29a(29) =10810800