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%I #12 Sep 08 2022 08:45:06
%S 1,5,53,115,3163,3263,170687,352399,1096397,223513,28103473,28459213,
%T 4963286677,5029541437,25532475569,51741301813,15299527769557,
%U 15415359085157,5677532668504877,1144538596366201,1156827116999161,1166157760248361,626832724103131129
%N Numerator of Sum_{k=1..n} phi(k)/k^2.
%H Vincenzo Librandi, <a href="/A072156/b072156.txt">Table of n, a(n) for n = 1..300</a>
%e 1, 5/4, 53/36, 115/72, 3163/1800, 3263/1800, 170687/88200, ...
%p with(numtheory); seq(numer(add(phi(k)/k^2, k = 1..n)), n = 1..25); # _G. C. Greubel_, Aug 25 2019
%t Numerator[Table[Sum[EulerPhi[k]/k^2,{k,n}],{n,30}]] (* _Vincenzo Librandi_, Nov 15 2011 *)
%o (PARI) a(n) = numerator( sum(k=1,n, eulerphi(k)/k^2));
%o vector(25, n, a(n)) \\ _G. C. Greubel_, Aug 25 2019
%o (Magma) [Numerator( &+[EulerPhi(k)/k^2: k in [1..n]] ): n in [1..25]]; // _G. C. Greubel_, Aug 25 2019
%o (Sage) [numerator( sum(euler_phi(k)/k^2 for k in (1..n)) ) for n in (1..25)] # _G. C. Greubel_, Aug 25 2019
%o (GAP) List([1..25], n-> NumeratorRat( Sum([1..n], k-> Phi(k)/k^2) ) ); # _G. C. Greubel_, Aug 25 2019
%Y Cf. A072157.
%K nonn,frac
%O 1,2
%A _N. J. A. Sloane_, Jun 28 2002
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