a(n) = Sum_{d|5} phi(d)*n^(5/d).

Terms

a(0) =0a(1) =5a(2) =40a(3) =255a(4) =1040a(5) =3145a(6) =7800a(7) =16835a(8) =32800a(9) =59085a(10) =100040a(11) =161095a(12) =248880a(13) =371345a(14) =537880a(15) =759435a(16) =1048640a(17) =1419925a(18) =1889640a(19) =2476175a(20) =3200080a(21) =4084185a(22) =5153720a(23) =6436435a(24) =7962720a(25) =9765725a(26) =11881480a(27) =14349015a(28) =17210480a(29) =20511265