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%I #12 Sep 30 2017 02:34:29
%S 2,4,10,18,46,100,204,420,840,1708,3478,7066,14286,28772
%N Number of zeros of the polynomial Sum_{j=0..n-1} z^(2^j-1)outside the unit circle.
%H Karl Dilcher and Larry Ericksen, <a href="http://www.jstor.org/stable/10.4169/amer.math.monthly.122.04.338">The Polynomials of Mahler and Roots of Unity</a>, The American Mathematical Monthly, Vol. 122, No. 04 (April 2015), pp. 338-353.
%t Table[Length[Select[Flatten[Abs[z/.NSolve[Sum[z^(2^j-1), {j, 0, n-1}]==0]]], #>1&]], {n, 3, 13}] (* _Vincenzo Librandi_, Sep 30 2017 *)
%Y Cf. A257592.
%K nonn,more
%O 3,1
%A _N. J. A. Sloane_, May 15 2015