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a(n) = (1/n) * Sum_{d divides n} (-1)^(n+d)*phi(n/d)*2^d.
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%I #7 May 23 2019 09:39:06

%S 2,1,4,4,8,10,20,34,60,100,188,348,632,1162,2192,4114,7712,14542,

%T 27596,52480,99880,190558,364724,699248,1342184,2580796,4971068,

%U 9587560,18512792,35790376,69273668,134219794,260301176,505286416,981706832

%N a(n) = (1/n) * Sum_{d divides n} (-1)^(n+d)*phi(n/d)*2^d.

%F G.f.: Sum_{k>=1} phi(k)*log(1/(1 + 2*(-x)^k))/k. - _Ilya Gutkovskiy_, May 23 2019

%Y Cf. A000010, A000031, A038063.

%K nonn

%O 1,1

%A _Vladeta Jovovic_, Sep 06 2002