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

Terms

a(0) =1a(1) =17a(2) =163a(3) =529a(4) =2501a(5) =2771a(6) =14407a(7) =16913a(8) =39529a(9) =42517a(10) =146411a(11) =86227a(12) =342733a(13) =244919a(14) =407663a(15) =541201a(16) =1336337a(17) =671993a(18) =2345779a(19) =1323029a(20) =2348341a(21) =2488987a(22) =6156503a(23) =2756819a(24) =7815001a(25) =5826461a(26) =9605467a(27) =7621303a(28) =19803869a(29) =6930271