[seqfan] Re: A049310 (by way of moderator)

[L. Edson Jeffery]

"If x = s + 1/s, then
S(N,x) = (s^(N+1)-s^(-N-1))/(s-1/s) = Sum_{k=0..N} s^{-N+2k}
Thus for x = 2*cos(t), s = exp(i*t),
S(N,x) = sin((N+1)*t)/sin(t).
If t = k*Pi/n, then S(N,x) is periodic in N with period 2*n."

Robert,

Thank you for that proof. Exactly what I needed. Very nice.

Ed Jeffery