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%I #15 Sep 06 2020 03:46:41
%S 1,1,-1,3,1,1,-5,1,7,1,-5,7,1,1,-13,15,-11,13,-9,11,1,1,-17,-1,21,-23,
%T 11,15,1,1,-29,31,1,1,-29,31,1,1,-29,31,1,1,-21,-7,31,1,-41,1,3,41,
%U -25,27,-47,49,-41,43,1,1,-29,31,1,-41,-19,63,1,1,-33,35,1,1,-65,67,1,-59,23,39
%N Differences between successive squarefree kernels.
%H Amiram Eldar, <a href="/A076334/b076334.txt">Table of n, a(n) for n = 1..10000</a>
%F a(n) = A007947(n+1) - A007947(n).
%F G.f.: -1 + (1 - x)*Sum_{k>=1} phi(k)*mu(k)^2*x^(k-1)/(1 - x^k). - _Ilya Gutkovskiy_, Apr 15 2017
%t Drop[CoefficientList[Series[-1 + (1 - x)*Sum[EulerPhi[k] MoebiusMu[k]^2*x^(k - 1)/(1 - x^k), {k, 100}], {x, 0, 100}], x], 1] (* _Indranil Ghosh_, Apr 16 2017 *)
%o (PARI) x='x+O('x^100); Vec(-1 + (1 - x)*sum(k=1, 100, eulerphi(k)*moebius(k)^2*x^(k - 1)/(1 - x^k))) \\ _Indranil Ghosh_, Apr 16 2017
%Y Cf. A007947.
%K sign
%O 1,4
%A _Reinhard Zumkeller_, Nov 06 2002
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