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a(n) = Sum_{d|n} n^(n^2/d).
0

%I #6 Oct 03 2021 10:38:40

%S 1,20,19710,4295033088,298023223876956250,

%T 10314424798490637108305446464,

%U 256923577521058878088611477224235622145150,6277101735386680763835789423286894578616620063532571951104,196627050475552913618075908526912116283103450944214825077052418578026469007467

%N a(n) = Sum_{d|n} n^(n^2/d).

%t Table[Sum[n^(n^2/i)*(1 - Ceiling[n/i] + Floor[n/i]), {i, n}], {n, 10}]

%o (PARI) a(n) = sumdiv(n, d, n^(n^2/d)); \\ _Michel Marcus_, Oct 03 2021

%Y Cf. A066108, A308593.

%K nonn

%O 1,2

%A _Wesley Ivan Hurt_, Oct 02 2021