a(n) = Sum_{k=1..n} lcm(k,n)/gcd(k,n).

Terms

a(0) =1a(1) =3a(2) =10a(3) =19a(4) =51a(5) =48a(6) =148a(7) =147a(8) =253a(9) =253a(10) =606a(11) =352a(12) =1015a(13) =738a(14) =960a(15) =1171a(16) =2313a(17) =1263a(18) =3250a(19) =1869a(20) =2803a(21) =3028a(22) =5820a(23) =2784a(24) =6301a(25) =5073a(26) =6814a(27) =5458a(28) =11775a(29) =4798