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2^(n-1) times coefficient of x in (1+x)^n mod U(n,x), U the Chebyshev polynomials.
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%I #5 Apr 30 2014 01:27:40

%S 0,4,14,32,77,192,452,1024,2299,5120,11270,24576,53241,114688,245768,

%T 524288,1114103,2359296,4980746,10485760,22020085,46137344,96469004,

%U 201326592,419430387,872415232,1811939342,3758096384,7784628209

%N 2^(n-1) times coefficient of x in (1+x)^n mod U(n,x), U the Chebyshev polynomials.

%F Apparently, a(n+1) = (n+1)2^n - (n+2)/4 * (I^n + (-I)^n).

%F Empirical g.f.: x^2*(x+2)*(x^2-2*x+2) / ((2*x-1)^2*(x^2+1)^2). - _Colin Barker_, Jul 16 2013

%Y Cf. A099586.

%K nonn

%O 1,2

%A _Ralf Stephan_, Oct 24 2004