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%I #18 Feb 13 2021 14:51:20
%S 672,30240,32760,2178540,23569920,45532800,142990848,459818240,
%T 1379454720,14182439040,43861478400,51001180160,66433720320,
%U 153003540480,403031236608,704575228896,13661860101120,181742883469056,6088728021160320,14942123276641920,20158185857531904
%N Numbers k such that both sigma_{-1}(k) > 2 and sigma_0(k)/sigma_{-1}(k) are integers.
%H Wikipedia, <a href="https://en.wikipedia.org/wiki/Multiply_perfect_number">Multiply perfect number</a>
%H Wikipedia, <a href="http://www.wikipedia.org/wiki/Harmonic_divisor_number">Harmonic divisor number</a>.
%e a(1) = 672 is the smallest number k that is both an Ore number and multiperfect such that sigma(k)/k > 2.
%t Module[{a166069 = {120, 672, 30240, 32760, 523776, 2178540, 23569920, 45532800, 142990848, 459818240, 1379454720}, i, n, result = {}}, For[i = 1, i <= Length[a166069], i++, n = a166069[[i]]; If[Mod[DivisorSigma[0, n], DivisorSigma[-1, n]] == 0, AppendTo[result, n]]]; result]
%Y Intersection of A001599 and A166069.
%Y Cf. A007691, A325025.
%K nonn
%O 1,1
%A _David Terr_, Jan 24 2021
%E Name changed by and more terms from _Jinyuan Wang_, Feb 11 2021