a(n) = Sum_{k=1..n} sigma( (n/gcd(k,n))^3 ).

Terms

a(0) =1a(1) =16a(2) =81a(3) =270a(4) =625a(5) =1296a(6) =2401a(7) =4362a(8) =6639a(9) =10000a(10) =14641a(11) =21870a(12) =28561a(13) =38416a(14) =50625a(15) =69890a(16) =83521a(17) =106224a(18) =130321a(19) =168750a(20) =194481a(21) =234256a(22) =279841a(23) =353322a(24) =391245a(25) =456976a(26) =538071a(27) =648270a(28) =707281a(29) =810000