a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} gcd(x_1, n)/gcd(x_1, x_2, x_3, n).

Terms

a(0) =1a(1) =11a(2) =43a(3) =115a(4) =221a(5) =473a(6) =631a(7) =1139a(8) =1609a(9) =2431a(10) =2531a(11) =4945a(12) =4213a(13) =6941a(14) =9503a(15) =10867a(16) =9521a(17) =17699a(18) =13339a(19) =25415a(20) =27133a(21) =27841a(22) =23783a(23) =48977a(24) =39721a(25) =46343a(26) =55555a(27) =72565a(28) =47909a(29) =104533