a(n) = Sum_{k=1..n} sigma( (n/gcd(k,n))^4 ).

Terms

a(0) =1a(1) =32a(2) =243a(3) =1054a(4) =3125a(5) =7776a(6) =16807a(7) =33818a(8) =59289a(9) =100000a(10) =161051a(11) =256122a(12) =371293a(13) =537824a(14) =759375a(15) =1082386a(16) =1419857a(17) =1897248a(18) =2476099a(19) =3293750a(20) =4084101a(21) =5153632a(22) =6436343a(23) =8217774a(24) =9768745a(25) =11881376a(26) =14408187a(27) =17714578a(28) =20511149a(29) =24300000