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

Terms

a(0) =1a(1) =22a(2) =105a(3) =414a(4) =745a(5) =2310a(6) =2737a(7) =7134a(8) =9231a(9) =16390a(10) =15961a(11) =43470a(12) =30745a(13) =60214a(14) =78225a(15) =118238a(16) =88417a(17) =203082a(18) =137161a(19) =308430a(20) =287385a(21) =351142a(22) =291985a(23) =749070a(24) =481245a(25) =676390a(26) =767391a(27) =1133118a(28) =731641a(29) =1720950