A373004 a(n) = Sum_{k=1..n} sigma( (n/gcd(k,n))^n ).
1, 8, 81, 1054, 15625, 279936, 5764801, 134480378, 3486843447, 100000000000, 3138428376721, 107006262884442, 3937376385699289, 155568095557812224, 6568408355712890625, 295150156996346511346, 14063084452067724991009, 708235345964697414795264
Offset: 1
Keywords
Programs
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PARI
a(n) = sumdiv(n, d, eulerphi(d)*sigma(d^n));
Formula
If k is squarefree (cf. A005117) then a(k) = k^(k+1).
a(n) = Sum_{d|n} phi(d) * sigma(d^n).