a(n) = Sum_{1 <= x_1, x_2, x_3 <= n} sigma( ( n/gcd(x_1, x_2, x_3, n) )^3 ).

Terms

a(0) =1a(1) =106a(2) =1041a(3) =7218a(4) =19345a(5) =110346a(6) =136801a(7) =465522a(8) =768327a(9) =2050570a(10) =1947121a(11) =7513938a(12) =5226481a(13) =14500906a(14) =20138145a(15) =29822066a(16) =25640641a(17) =81442662a(18) =49651921a(19) =139632210a(20) =142409841a(21) =206394826a(22) =154751521a(23) =484608402a(24) =302749845a(25) =554006986a(26) =560366223a(27) =987429618a(28) =616040881