This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A320974 #4 Oct 25 2018 17:26:36
%S A320974 1,5,28,272,3126,47450,823544,16842752,387440172,10009766650,
%T A320974 285311670612,8918294011904,302875106592254,11112685048647250,
%U A320974 437893920912786408,18447025548686262272,827240261886336764178,39346558271492178663450,1978419655660313589123980
%N A320974 a(n) = n^n * Product_{p|n, p prime} (1 + 1/p^n).
%H A320974 Wikipedia, <a href="http://en.wikipedia.org/wiki/Dedekind_psi_function">Dedekind psi function</a>
%F A320974 a(n) = [x^n] Sum_{k>=1} mu(k)^2*PolyLog(-n,x^k), where PolyLog() is the polylogarithm function.
%F A320974 a(n) = Sum_{d|n} mu(n/d)^2*d^n.
%F A320974 a(n) = A320973(n,n).
%t A320974 Table[n^n Product[1 + Boole[PrimeQ[d]]/d^n, {d, Divisors[n]}], {n, 19}]
%t A320974 Table[SeriesCoefficient[Sum[MoebiusMu[k]^2 PolyLog[-n, x^k], {k, 1, n}], {x, 0, n}], {n, 19}]
%t A320974 Table[Sum[MoebiusMu[n/d]^2 d^n, {d, Divisors[n]}], {n, 19}]
%Y A320974 Cf. A001615, A008683, A065958, A065959, A065960, A067858, A320973.
%K A320974 nonn
%O A320974 1,2
%A A320974 _Ilya Gutkovskiy_, Oct 25 2018