a(n) = Sum_{1 <= x, y <= n} lcm(x, y).

Terms

a(0) =1a(1) =7a(2) =28a(3) =72a(4) =177a(5) =303a(6) =604a(7) =948a(8) =1497a(9) =2127a(10) =3348a(11) =4272a(12) =6313a(13) =8119a(14) =10324a(15) =13060a(16) =17701a(17) =20995a(18) =27512a(19) =32132a(20) =38453a(21) =45779a(22) =57440a(23) =64664a(24) =77689a(25) =89935a(26) =104704a(27) =117948a(28) =141525a(29) =154755