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%I #9 Sep 08 2022 08:45:06
%S 1,17,1409,11353,7137097,7147097,17199059897,137714029801,
%T 3721352084627,3722696337299,54537603391194659,54547094712264659,
%U 1558510008178113485699,1558729492839246365699,1558951562903235322883,12472984853932601449939
%N Numerator of Sum_{k=1..n} phi(k)/k^4.
%H G. C. Greubel, <a href="/A072160/b072160.txt">Table of n, a(n) for n = 1..585</a>
%e 1, 17/16, 1409/1296, 11353/10368, 7137097/6480000, 7147097/6480000, ...
%p with(numtheory); seq(numer(add(phi(k)/k^4, k = 1..n)), n = 1..25); # _G. C. Greubel_, Aug 26 2019
%t Table[Numerator[Sum[EulerPhi[k]/k^4, {k, n}]], {n, 25}] (* _G. C. Greubel_, Aug 26 2019 *)
%t Accumulate[Table[EulerPhi[n]/n^4,{n,20}]]//Numerator (* _Harvey P. Dale_, Nov 15 2020 *)
%o (PARI) a(n) = numerator(sum(k=1, n, eulerphi(k)/k^4)); \\ _G. C. Greubel_, Aug 26 2019
%o (Magma) [Numerator( &+[EulerPhi(k)/k^4: k in [1..n]] ): n in [1..25]]; // _G. C. Greubel_, Aug 26 2019
%o (Sage) [numerator( sum(euler_phi(k)/k^4 for k in (1..n)) ) for n in (1..25)] # _G. C. Greubel_, Aug 26 2019
%o (GAP) List([1..25], n-> NumeratorRat( Sum([1..n], k-> Phi(k)/k^4) ) ); # _G. C. Greubel_, Aug 26 2019
%Y Cf. A072161.
%K nonn,frac
%O 1,2
%A _N. J. A. Sloane_, Jun 28 2002
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