%I
%S 2,3,4,5,6,7,21,26,99,158,405
%N Numbers n for which the absolute value of the discriminant of the polynomial x^n  x^(n1) ... x  1 is a prime times 2^k for some k >=0.
%C This polynomial is the characteristic polynomial of the Fibonacci and Lucas nstep recursions. Are the nstep recursions different  in some way  for the values of n that yield a prime*2^k discriminant? No other n < 10000.
%D Mohammad K. Azarian, On the Hyperfactorial Function, Hypertriangular Function, and the Discriminants of Certain Polynomials, International Journal of Pure and Applied Mathematics, Vol. 36, No. 2, 2007, pp. 251257. Mathematical Reviews, MR2312537. Zentralblatt MATH, Zbl 1133.11012.
%H Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/FibonaccinStepNumber.html">Fibonacci nStep</a>
%Y Cf. A106273 (discriminant of the polynomial x^nx^(n1)...x1).
%K hard,more,nonn
%O 1,1
%A _T. D. Noe_, May 02 2005
